The whole thing is difficult. I am dealing with an excellent gas lighter myself. I ended things with him about six weeks before he left me (he told me what I wanted to hear on Valentine's Day and we made up, I'm such a sucker) and managed to shift blame so well that I basically begged him to come back, completely forgetting that I wanted to end things in the first place!
The manipulation is no joke... it really messes with your mind. I know what you mean about no remorse. I got a, "I didn't mean to hurt you", after eight years and a heinous discard. Sometimes I think the booze takes over their soul...