Dunno if anything I have to say will make much sense or be much help, seeing as how I'm dealing with my own sense of impending doom right now, but I'll give it a shot anyway....
Well first of all, I think you need to focus on forgiving yourself for the A. Yes it was a stupid mistake, but you realise that and want to make amends. If you can't forgive yourself and accept yourself, then how can you ever expect your H to do the same?
As for being selfish by staying in the same house as him, I don't know that I'd go that far. You are, afterall, there to be with your D, and not just with him, and I'm sure your D enjoys having you around.
I don't suppose the house has any spare bedrooms that you (and possibly your D) could move into? I know in your first post you said that all 3 of you sleep in the one king size bed, so it may very well be that there isn't anywhere else in the house you could sleep. If there is though, then perhaps you could arrange to have separate rooms, so that you could both still be under the same roof with your D, but you could still each have your own space as well.
Me:30 H:30 Together:10yr H left:Oct3'06,couple weeks before 5th wed anniv. No Kids OW bomb:Jan19'07 My thread: He filed.