Deedee, I understand the feeling of hope that "he is still in there". I felt it too with my SO/ex-SO, but the truth is, they're not, at least not in the sense you're convincing yourself of. He's never going to become what he was again, that is part of him, but so is this. He may have moments where he behaves like he used to but you need to open up to the fact that this is also who he is, don't sit there hoping the old him comes back, he won't.
I've had to learn that, my (probably now ex) SO has completely changed in the past 2 months, we don't even talk now. I have been so sad and down but I know now I am grieving what we HAD and what she WAS, I've come to accept that she will never be that again. She may behave that way again sure but now everything is different. I can't trust she won't also slip back into this behaviours, the way she's acted has changed everything I feel in terms of trust.
You're begging us to help you hang on, just think about that.
Why should you be hanging on to anybody? Aren't you worth more than that? I'd like to think you are, I'd like to think we all are. There are boundaries and we have to establish and accept them, or else the "sufferers" will take liberties forever and we will suffer. It's awful and it may mean your relationship ends, but you can't just sell yourself short for them forever, it will absolutely destroy you.