I'm thinking no XP. It was a meager source anyway. Or perhaps you get XP each time you lower your trust in someone.

For Apocalypse World I prefer 2 or 4 players. I like doing small scenes and for some reason leaving half the players out feels right but leaving 1/3 out doesn't feel right.

Take a cue from actual religious people and do batshit insane things in private but be normal in public.

One of the coolest things I've seen in Apocalypse World was how a Skinner who was the eternal tease after several sessions (at which point she had something like 5 courtiers who were all proper NPCs she had sunk her claws in) got the cult advance. Obviously her cult was her courtiers, they just didn't know it. Obviously their surplus was violence when they started beating each other up and challenging each other to car duels and whatnot.

Doesn't Rasmus represent the typical Faceless mobster you murder?

1st situation:

I would have handled it as a Size by force roll. The hard advance from the leadership is what makes you able to do that roll at all! Definite hold would have been driving them into the sea.

Generally:
What makes fighting zombies different here than fighting people? I guess their gangs do no break after X harm. How organized are they? If they fight with coordination the optional battle moves could work well defending a position etc.

2. What do you mean by "catch the awe of the creature"? Like: When you announce you are the creature's creator, it will cower before you in awe? Or like: When you exert your will over one of your creations, it must obey you, flee, or rebel, and if it rebels, you get +1 ongoing until you defeat it or it manages to escape (?)

3. So would you say that T'sais is "predatory"?
(It feels a bit euphemistic-y to me, I would go with "hostile" for a general word or straight-up "hates life" for her specifically.)

The list you've got right now is pretty good, but I'm wondering if something like this would also be interesting and have some extra replay value:

Before you begin playing, write a specific trait next to each of the general weaknesses. You or the MC can add this trait to a vat-creature you make:
crippled: _________
dependent: _________
hostile: _________
psychic: _________
uncommunicative: ________
weak: _________

And then each time somebody plays a vatlord, they will have a different starting list, and more specific traits to add to their creations. Might be too complicated, though, especially considering part of the fun is collecting traits from other characters.

2. Basically I want to explore how the player handles the creatorhood. Do they consider their creations children, slaves, equals? If they try to control their creations do they do so by seduction, threats, manipulation or something else? With your move the reaction would be up to the creation and the MC would have to spend brain resources coming up with a personality and stuff, with normal moves a personality will snowball forth. With the simple +1 they can do whatever they like but they'll still do it better than anyone else. Can you come up with a way to do that? If the move is too ugly just not having it might be better.

3. She is a perversion of birth (impulse: craves overthrow, chaos, the ruination of all). Her vat traits would probably be beauty and insanity or maybe swordsmanship. A predator wants to victimize someone, might be skirting threat impulse but I've seen plenty of innocent grotesques.

Interesting thought but I love how AW-lists are limited, the only blanks I remember are for filling in the names of people.