So your husband and his gf want you and your husband to get divorced so that they can be together but he doesn't want you persuing any other relationships? That seems completely unfair to me and that you're really getting the short end of the stick here. I wouldn't stand for it. From what you've said here it sounds like you're letting them walk all over you.
If I were you in the situation you're in now I would plan on getting my own place and setting up date nights with your current-soon-to-be-ex husband. If you have your own space it might be easier to make that boundary clear that you don't belong to him. You are your own person and you should be able to persue relationships that make you happy. I don't think it is healthy for you to stay living with him until the absolute last minute. It's probably going to be easier to start your own life now as an independant person.
I'm not seeing a lot of respect here towards you at all. If he still does want a relationship with you I think he should put some effort into wooing you again. If he's not willing to, move on. There's going to be someone(s) out there who will value and respect you. Don't just hang out being the stop gap until he can be with her full time. That's not fair to you. It's not up to you to fill a gap in his life. If this is the call that he has made then maybe he should be spending some time alone.
Everything will be ok in the end. If it's not ok it's not the end.