Damn. This is a clever way to get the players invested in game, as well as into the Psychic Maelstrom component of the game. Good show!

Love letters threw me off initially: I found they are best used as lead-ins for a pre-gen, one-shot game (like at a convention), or to hand-wave time passing in the game while still giving the players impact on the world/plot/etc. Which is not to say you can't do it whenever you opt to.

When I first started out, I had this conception that the base setting of Apocalypse World was a "Mad Max"-style wasteland, and I rolled with that. In truth, the setting  can be however you want to spin it. I ended up editing it to be a more temperate wasteland set in Paso Robles, using local landmarks as inspiration (I needed a plausible military base in proximity).

The AW book says to stay true to your research, but if the players improvise a setting detail on their own - a detail which may contradict something that you have technically already written down somewhere in your brainstorming, but have not yet shown "on screen" - then you are free to edit/replace/whatever and go with what the players suggest. The players' suggestion will ensure more investment in the setting, and you can possibly re-introduce your cool idea elsewhere.

That said: if you've already established an element of the fiction, then don't retroactively change it, unless circumstances make it feasible. Your NPCs are always in your crosshairs, someone can always start polluting the "clean" river nearby, and a faceless post-apocalyptic technology-hoarding enclave can always start releasing mutated spidercats into your players' neighborhood.

So, as to "I am Legend": I found many apocalyptic images online, and the ones which fascinated me most were the ones in large urban centers, with lots of tall buildings, much like the setting of "I am Legend". I am also a veteran of the "Fallout 3" and "Fallout: New Vegas" games, so I am experienced with the look and feel of traveling through sprawling urban wastelands. So many options for ecologies, environmental hazards, resources, territorial conflict, surprise attacks, and more.

So if I had to do it again, I would opt for a more urban setting for my Apocalypse World game, something with a lot of gutted office buildings or skyscrapers, something which would allow me to include a diverse array of locations: parks, buildings, subways, car-choked roadways, hospitals, factories, and more. I think your idea has a lot of possibilities.

The way Monsterhearts (for example) handles it is that you only benefit from one highlighted stat in a given scene - perhaps the pre-game rolls count as a single scene (or not really a scene at all?). Technically, each roll comes with a risk, right, so putting your hand in a meat grinder twice may be worth the experience? YMMV.

As for solutions: if the other players feel it is unfair, they can always choose to highlight one of the Hardholder's (or the Quarantine's, in your case) other stats, and then it is the GM's option to then highlight something: if the GM opts to highlight the Quarantine's Weird or the Hardholder's Hard, the GM is making the choice to level faster, not mix things up.

I use a mind map in XMind to track NPCs, vehicles, notes, damage, and such in my AW game. I created a set of icons to go with Apocalypse World:
1) the countdown clock at each iteration
2) miscellaneous post-apocalyptic iconography (fortress, male, female, raider, group, vehicle)

This .xmp file can be imported into XMind so you can use those icons:
https://docs.google.com/open?id=0B5aCjfAHYXoQbGE5OGo2OVRPQW8

How many folks are using real-world recovery times in their AW games?

Because if that's the case, over time people are not going to go see the Angel anymore for minor injuries, since a) they heal on their own over time (a suggested guideline of up two one segment per session), and b) when they do see the Angel, it becomes a case of "lie down for a week, or I'm going to make up some new complications related to your injuries which haven't come up just yet".

Thankfully, this is a moot point.

To use it to stabilize and heal someone at 9:00 or past: roll+stock
spent. On a hit, they will stabilize and heal to 6:00...

An Angel Kit can *only* heal you back to 6 o'clock (2-harm) so you only seek out an Angel if you are at 9 o'clock or worse. If you are only at 3 o'clock or 6 o'clock (1- or 2-harm), an Angel Kit *cannot* help you, so that situation wouldn't come up.

That said, an Angel with Healing Touch *can* take away additional harm and leave the patient at 3 o'clock or even 0 o'clock, but there aren't recuperation penalties associated with that. Just potential mindfuckery from the Maelstrom.

I'd still like more info on how they must "do their time", but the question of going to the Angel when you are only suffering 1- or 2-harm is not an issue in this case.

We may want to take a page from FATE and treat some of these conditions (well-armed, blissed out on chillstabs, fighting through the pain) as Aspects that we can more or less tag for free, depending on the narrative.