Just got into the game... Where do I start?

First of all, I love the idea of this game.
A gritty, darker version of fallout, with malleable roleplaying elements and infinite possibilities that is narratively driven... the idea is quite unique.

And yet, while it's amazing, I have no idea how to begin playing Apocalypse World, or "living" within the rules of the established systems... because I don't understand many of them!
Here are my issues so far, maybe you guys can help me with a few of them:

-How do I find a group and begin playing the game? (Skype and Roll20?)

-Are the character creation templates set in stone? (E.g., no customizing Drivers to ACTUALLY have another car that's a tank?)

-Do NPC's ever have PC characteristics? (e.g., perks, can take harm levels up to 12, classes of their own, etc.)

-Is the Maelstrom the equivalent of the WH40K Warp? (All-encompassing, corrupting, but utterly inscrutable?)

-What the fk can the Maelstrom do? (Anything/Everything?) Can it manifest physical objects, or just incorporeal visions? Or is that up to the MC?

-Does everybody always have to be an asshole to each other, in true Fallout style? (Hello Courier, welcome to Vegas, now fuck off and die in a hole)

-If the setting is only 50 years after the Apocalypse, where the Fuck did all of the tech go? Did the Apocalypse contain global EMP's resulting from STAR WARS satellites set up to (unsuccessfully) prevent global thermonuclear war? Is there an unnamed organization like the Enclave or the BoS that nobody talks about or fucks with? Or did a magical Tech bunny eat it all in his quest for world dominance?

I think you'll have to ask the characters about the maelstrom when you get a game going. They should know, they grew up with it.

Why do you want to customize the play books?

Why do you want to give NPCs the characteristics of PCs?

There's no rule that everyone has to be an asshole to each other.

The asymmetry between NPCs and PCs is an important part of the game. It's a mechanical asymmetry. The thing is, PCs roll, so they need stats. You can have an NPC be anything you like -- you're the MC. "Classes of their own" -- well, they sort of already have "classes" -- threat classes: Warlord/Alpha Wolf, Brute/Sybarite, and so on. You can give them moves, too, but there are two types of moves -- MC moves, which are just "reminders to the MC to do something", and don't have mechanics (so like "reveal the secret beneath the caves" or "summon the nanite swarm" would be MC moves relating to a specific NPC), and PC moves. You can create PC moves tied to a specific NPC, but the PC still rolls. ("When you're attacked by the nanite swarm, roll+weird. On a hit...")

 So you can make your NPCs be anything you want, but they don't look, mechanically, like PCs. They look like threats, because they're yours.

If you want to give them more harm levels you can, but remember to look at everything that's yours through crosshairs. Ask yourself, why do you want this NPC to be physically hard to kill? That may sound like a silly question if you're used to games where killing the level-boss monster is a matter of whaling away with attack after attack, chipping away hit points while surviving its attacks until it succumbs to attrition. But AW is designed to avoid that kind of lots-of-the-move-in-a-row battle, because it's seen as kind of boring. (Even Dungeon World, which is AW hacked to a classic D&D setting, avoids this: cf. http://www.latorra.org/2012/05/15/a-16-hp-dragon/ )AW is much more about a volatile situation with no status quos. Want to kill the big bad NPC? Ok, he's dead. Now you have to deal with the consequences of that. Maybe they're even worse. This is not to say that there's never an NPC who's hard to kill, but usually it's more interesting than "he just has a lot of hit points". It's more that he's hard to get at, that achieving the fictional positioning required to be able to make that seize or go aggro move is the hard part. Maybe his gang's in the way, maybe he's got leverage which makes taking him out dangerous, maybe he has a custom move -- "Rudder always knows you're going to hit her a few minutes before you do. When you seize or go aggro on Rudder, roll+sharp. On a 10+, you've managed to fool her about exactly when or how, though she still knows it's coming; go ahead and do the move, but take -1. On a 7-9..." and so on.

You can certainly customize playbooks (technically, you're either adding PC-specific custom moves to your homefront, or starting your own mini-hack, either of which is heartily encouraged) but, again (and as noclue said), think about why. Might be worth playing with the constraints of vanilla AW first. Might be that you can achieve what you want with the playbook and its advances. Might be that you can achieve it in the fiction (maybe the Driver ought to go take that tank, on table, away from whoever's currently got it).

The examples in the rulebook do highlight a lot of merciless PVP that gives you the sense that everyone is an asshole to each other, but I think play is most interesting when there's a mix of assholery and not-assholery. Characters who are simply all perfectly loyal to each other, and characters who are simply constantly amorally out to screw each other, are both more limited a scope for story than characters who have urges that both unite and divide them. Vincent is on record somewhere saying that he expected AW PCs to interact like the characters in Firefly -- at each other's throats a lot of the time, but always ready to unite in the face of greater dangers. The campaign I've been running is more PVP than that, but still with plenty of room for alliances and morally-gray antihero moments of selfless nobility.

As for what the maelstrom is and can do, and what happened to the tech, and so on, for one thing, what noclue said -- ask the PCs. But also, maybe the PCs don't really know that much, maybe it's a mystery to them too -- they live in the presence of the maelstrom and make some accomodation with it, but don't know what it's actually capable of, or what the hell happened. I suggest you play to find out. That means it's an emergent result of the characters' actions; neither the players, nor the MC, knows going in. The rules say you find out what's beyond the maelstrom when a character takes advanced open your brain and hits a 12+ -- and, the rules say, "I envy you finding out."

Check out this thread: http://apocalypse-world.com/forums/index.php?topic=6587.0 for a discussion of various takes on the maelstrom and on playing to discover what it can do.

(Interestingly, my take after reading the rulebook was not "where did all the tech go" but rather "50 years out, why is there so much left?" Biker gangs with ample gasoline, ammo to spare, cans of peaches, violation gloves in working order? Hardly anyone I know IRL knows enough to make a bow and arrow, never mind maintain a motorcycle without an international supply-chain for parts. If our current house-of-cards technological society collapses, I'm imagining a lot LESS tech 50 years out....)

NPCs don't have to be assholes, but they do have to be Threats. An important distinction; often a friendly or well-meaning NPC constitutes a much graver and more dangerous threat to the PC's way of life than just another dickwad with a gun.

Everything to do with the Maelstrom is up to the MC and players to determine, usually in collaboration. But basically the Maelstrom can do anything, as long as whatever it does is in accordance with the MC's principles and agenda. Which includes "make Apocalypse World seem real", so consistency and precedent are a big deal when it comes to Maelstrom activities.

Given that the PCs can acquire an advancement that allows them to "see through" the Maelstrom on a 12+, it is certainly not inscrutable.

The previous posts have talked a lot about the maelstrom, and I think the answer of "it can do whatever you and the players decide it can do" is the best advice.  I know that seems like a cop-out, but trust me, it's better this way.  People come into the game with different expectations and biases.  Asking your players how they interact with the maelstrom when they first open their minds to it gives you as the MC a little window into those expectations and biases, and lets you shape your world accordingly.  If all of your players think of it as a 40K-style "Warp," then their descriptions will tell you that.  If some of them view it as "the spirit world," then their descriptions will tell you that too.  And if it's "the will of the gods," or "an alternate dimension seen through a smoky glass," then that's fine too.  And each of these games will be very different and have different things of which the resulting communally-defined maelstrom is capable.

In terms of playbooks for NPCs, what you're really looking at are custom moves, not for the NPCs themselves (because the MC never rolls dice) but rather for the PCs when they interact with those NPCs.  So for instance, you talk about different levels of tracking Harm.  Here's a potential custom move for a Warlord threat, let us call him The Humungus.

The Humungus is one tough sonofabitch.  He tracks Harm like a PC.  Any time the Harm inflicted on the Humungus goes past 9:00, roll+Hard.  On a 10+ he takes the Harm as established.  On a 7-9, his Harm is limited to 9:00, but pick one:
* The Humungus is shattered: The Humungus loses his taste for the fight, at least for now. He flees/retires/pauses to lick his wounds. Create a new threat countdown for The Humungus starting at 0:00 - he fucks off until that counter is filled. Advancing this clock a tick is now a Threat move.  (This gives the players a reprieve from the predations of this particular Warlord threat for a while).
* The Humungus is crippled: The Humungus breaks and shows weakness. Some of his warriors take this as a sign that he's not fit to lead and break away from him. Reduce the size of The Humungus's gang from large to medium. A cruel MC could add one or two new small gangs as emergent threats, or not. (Either way, it reduces the size of the rampaging horde and exposes them to the possibility of defeat in detail.)
* The Humungus is disfigured: The Humungus loses most of his nose, making him one ugly dude and giving his voice a reedy quality. He is surprisingly self-conscious about it, and players may take +1 in any moves against him where cracks about his appearance can be brought into play (such as Acting Under Fire to defy his will - "Bring me your women." "That's tough talk from a dude who sounds like a cracked flute").
* The Humungus is broken: The Humungus has taken a pretty serious blow to the head. He wasn't all there before, and now he's mostly somewhere else. The players take an +1 forward any time they are making a move to outsmart The Humungus. (This gives crafty players a better chance to defeat The Humungus using cleverness rather than straight-up brute force, or at least to maneuver him into a position where force will be more effective).
On a miss, he's so damn tough that damage past 9:00 is discarded.

This makes the NPC a little bit tougher individually, but also includes mechanics to alter how he functions or make him a recurring villain.  But again, this is all driven by the players' rolls and choices.  You can also stack moves. This is really common in Dungeon World, where getting close enough to attack a particular monster might require you to first defy danger.  In Apocalypse World, that could be something like:

Amano is unnaturally crazy sexy hot.  Any move made against her is made under fire.

In other words, the PCs need to first roll+Cool, taking the consequences of that roll before doing whatever it was that they wanted to do.  But make sure this plays out in the fiction.  Describe how Amano's aura of distracting sensuality influences or unsettles them (or the situation around them).  That's where the magic of custom moves for NPCs comes in - in how they influence not only the mechanical effects but in how they affect the fiction.

Stat substitution can be fun too.  You could apply this in many different ways, like:

Amano's emotions are like an open smut novel: attempts to read her roll+Hot instead of +Sharp.

or:

Jackson Twain has bizarre and inscrutable urges: roll+Weird when trying to manipulate him, nor do attempts to give 1-barter, but with strings attached have any effect on him.  The dude is just not motivated by ordinary wants.

Stat substitution really comes into its own when one of a particular PCs' primary foils has a substitution move that hits that PC's lowest stat.  So if I have decided that Hot is my dump stat, I am going to have a hard time figuring out what Amano is up to, and maybe I should recruit the Skinner to help me out.  Or if I have -1 Weird and I need something from Jackson Twain, maybe I should convince the Brainer to get it for me.  This will encourage players to work together in interesting ways, and is a great way to set up PC-NPC-PC triangles.

And finally, other options can be mechanical but based on gear (or gear-like traits) rather than moves.  For instance, The Wyrd fights with a psychic knife.  All damage inflicted by him is 2-Harm hand ap.  Or, Riddler Jack is slippery and always counts as having 2-armor in combat at close range or less.