Jennie, I fully know that this is not a black and white issue and this is a hard decision to make.
That said, I think you should leave him...at least for awhile. This doesn't have to be The End. I think that the fact that you're moving is a GREAT thing. It can give you guys a chance to have space from the relationship while you're busy with new changes on another front.
You can't stay with a guy who physically attacks you, no matter how mild or how severe. But just because Bill has done this once doesn't mean that he necessarily will do it again. It doesn't mean that this one incident makes him an abuser who can never be in a relationship.
However: if you don't take a break from the relationship for awhile, I absolutely believe he will do it again. He needs to get professional help in order to get over this and he needs to get that without the context of you living with him.
Here are other reasons that the relationship may need a break, and I am taking this all from previous journal entries:
a) he is trying to persuade you to a more serious relationship than you are ready for, given your post on 2007-03-25 17:57. You used the words "he is pressuring me."
b)He is convinced that you are cheating, this has caused frequent disagreements and you yourself have slapped him in an argument. I magazine I read at the gym (if you can't trust that, what CAN you trust?!) quoted a marital counselor as saying constant worries that your partner is cheating is "corrosive" in a relationship.
c) You have to nag at him to get him to do the general mental health stuff, like take his meds, that he absolutely needs to do...at times he has gone weeks at a time without taking important medication. This all means that basically, he has a LOT of shit to work out, and it's super hard on a relationship, and maybe it would be kinder to give him the space to work on himself before he can handle being a boyfriend.
d) a few things you have said make me think that he is, not intentionally necessarily, encouraging you to overdue things with drugs and alcohol. This is just an impression and I totally could be wrong about this.
e) Previously, you have said that Bill "keeps trying to dump me" and that you're "sick of this." Given that your relationship is still pretty new, relatively, this worries me...
Anyway, I realize that I'm taking this stuff from a blog where you probably vent a lot of drama and keep the calm, good stuff quiet. Most relationships look unstable from that point of view, so it's kind of unfair. But all this stuff has happened with a guy in the course of less than a year, and well, I just think the best thing to do is to take a break.
Not to mention that if this relationship can be saved, it needs it. Just my humble and totally unprofessional opinion...
...no matter what you do, I love you and will support you in the action you choose to take.