It was a fun game!

I am curious about the intention of the double-circled options in the stronghold's armory, though.  Can those be bought at the one-circle level (like for 20 fighters) or the two-circle level or is it supposed to be as we ended up interpretting it, it just costs double?

It did seem funny when I turned out to be the only PC that was a member of the "local" people created first as a part of the stronghold.  Is it seeming typical for players to frequently just make up their own peoples?

Neat!  But a couple things:

The columns don't induce proper folding at least how it printed for me.  I'm not exactly sure what's wrong -- maybe the middle column needs to be slightly narrower?

Can you lay it out so that there's room under or next to the Hex move?

If you can't figure out what they're seizing, ask yourself if they're going aggro instead.  Do they want to take something or do they want to make someone do something?

As for taking damage from a defensible position, do you mean defensible or invulnerable?  Normally, particularly in post-apocalyptic settings, if you're in a position to deal damage, you're also in a position to receive it.  

When the player was diving out the window with guns blazing, what was the goal?  Surely not just to look cool?  To look cool while doing something would be my guess; what was that something?

Have you seen this thread?

When you say that the raider are opening up, your players are all going to say things -- exclaiming at the circumstance, and narrating how their characters are responding.  Some, maybe all, of those will involve a move.  They can all make a move, but they might not.  In a case like that, they probably all will.  Even if they're all diving into cover, you're likely going to call that acting under fire, right?  

You will not make a MC move for each of those.  If the players look to you to say something, then you'll make a move.  If the players roll a 6- on a move that doesn't list a specific result, then you'll make a move.  If the player offers you "the perfect opportunity on a golden plate," then  too, you'll make a move.

In the case where they're all shooting back, I've found it pretty rare that all the PCs in a game are in the same place at the same time and on the same side.  It's usually wildly more nuanced than that.  And if that's how things are generally rolling, it means you're not using PC-NPC-PC triangles effectively enough to drive wedges between them, so step up your game (I need to do that better, too).  But let's say this is one of those cases and they're all opening up.  It would be awkward to have them all roll to seize by force.  I suppose the way I'd do it is let the first person to speak up make the move and the others might help (or maybe interfere) based on their narrations.  Or I might make the PCs a gang and use the rules for that.  Or maybe both.  If there's anything left after that first seize, and the change in the fiction that comes out of it then maybe another of them will make that (or another) move.  And like you said, just exchanging harm might feel like the best application of  the rules; if they all say their shooting back, and they're looking to you to say something, instead of calling for a roll, you can just say, "OK, everyone takes two harm, your enemies are lying in a giant blood-slick, make the harm moves..." and go on.

On a failed seize by force you make an MC move.  If the most logical thing is that everyone takes harm, as established, do that.  If the tactical situation in the fiction calls for something else, do that.  If you can justify some other outcome and want to bring that in, instead, go for it.

The consumption of e.g. leadership hold will often coincide with a PC's move, but not always.  It might instead, direct what MC move you make.  If the hardholder wants to spend one hold on his away-team's hard advance in the face of withering fire, maybe he's not there to make the move himself, so you just decide that they're doing it (he did roll and get the hold, after all) and you assign harm to all sides as the fiction demands.  Or maybe she spends the hold to tell her normally undisciplined gang not to eat the survivors' skin and you figure it doesn't require a manipulate or pack alpha or whatever roll.  But the use of those hold might well make a move on the PC's part possible that wouldn't have otherwise been available.  It all depends on the fiction as established.

I've played a bunch of Apocalypse World and a bunch of IRC.  But haven't played AW over IRC, so take this for what it's worth.  I can't see any reason in the world that it would be particularly problematic.  I've played in great games over IRC with no GM prep.

What exactly did they think was stupid?  Why would an IRC game need prep any more than a F2F game?

I think it sort of depends what your point is and what the people you're making the game for find fun.  If the central facet of the game is this hunt and you dig all the differentiation, then the longer more explicit set of moves is fine.  It feels like too much to me from this uninvested vantage but I don't really know.  And we might prefer different things.