It's hard - I think giving an ultimatum can backfire temporarily, though in the end it might bring them back. There is no way to know.
During the time my ex-b had gotten mean, I was sure there was someone else at the time (and I was pretty sure I knew who it was). At that point it appears to have been an EA, later a *very* short-term PA, and I could tell when it was likely over because he came out of the anger towards me.
You can't always assume, but having another person in the picture can create anger. What I'd worry about is him saying that you were taking his air. He's feeling smothered, and you don't want that. Let him initiate anything. Tempt him, don't force him.
I know it's really difficult. I can't be around ex-b easily without wanting to attack him - so I don't try to start anything unless I think it is okay. I mean...I may flash him, I'll kiss him goodbye, but I won't jump him or give him large kisses or anything unless I feel he'll respond well. It's helped a lot, at least for now. And I dress sexier.
The thing though also is...you don't want him just sexually, but emotionally. There are moments I can feel I have ex-b in an emotional way - but other times he's closed off. You have to be inviting in every way. I've taken up more of ex-b's hobbies, and he's been really good to me these last few weeks. Even if it ends, I'm glad to have gotten him back for the last 10 months, and not had the last rememberance of him be that awful alien.
