I'll be blunt about this.

By the sound of it you will be better off without him. You asked if he would possibly get better. Well, has he gotten better by this point in his life? Chances are he will not change a single bit without some drastic effort on his part. It would seem that he has already decided that isn't going to happen.

I know it isn't easy but given your own description and suggestions by even his own family you should move on.

I am sorry to come off as a bit harsh in all of this but I don't see how he can possibly be a positive force in your life at this point. You have already given him 12 years to do better. Instead it sounds like you have gotten used to being treated worse. I say enough is enough, if he doesn't want the relationship any longer than maybe that end up being a benefit to you.

It sounds like with him gone you can do a better job of keeping your life going, have fewer problems and not have to deal with the constant disappointment, hurt, and abuse that he has brought on you.

I know it really isn't an easy thing but I would suggest letting him go his own way and you work on getting your life back to what you want it to be.

I hope things turn out well, good luck.