First of all, I want to let you know that the problems in your relationship are probably coming from both sides. I don't mean this to dismiss abusive behavior or victim blame by any means, however. (Beverly Engel's The Emotionally Abused Woman had some good insights that might help you too)
I have no idea if he has been with any one else long term. I don't ask our mutual friends about him, but sometimes they volunteer information or tell me that he asked about me. Now that I've been out of the relationship for so long (and am in a new relationship with a more emotionally stable person) I do feel like I can see clearly how I contributed to the problems in our relationship. I do feel like his issues would be present in another relationship as well (just like mine are). How those issues may manifest with someone else though, I don't know. All I can do is take care of myself and try to be aware of my issues, and work on that. I can definitely say that I do still miss him from time to time - mostly because of the things we used to do together and the bond we had in that way, but I do not miss the rest - not one bit. And the thing is it's a package deal. I can't just have one side of a person. I will say, also, that since I've been out of that relationship I have become a healthier person and am better able to take care of myself without the constant nightmarish stress looming over me every day, and I am also allowed the mental space to properly reflect on my own psychological problems and try to remedy that. Don't get hung up on the what-ifs. Just reflect on what is best for you both. You might already know the answer.