Please be careful that his vow to be a better person isn't a game. Sometimes people lay it on and it's really a way to keep misbehaving and then apologize. Don't tolerate any abuse from anyone. Make sure that he doesn't hate himself by being kind, considerate and in control. This may sound more like his way of saying he is sorry but it is best to not engage in behavior. He is trying to say that whatever he did is not typical behavior for him.
Also try not to be too accommodating. You deserve to be treated well and not otherwise followed by excuses. Bend but don't break for someone else. On the positive note, he may really want to change and thinks enough of you to be examining the way he behaves or thinks around you.
Try to find ways to interact with each other, and to be happy or as he says not miserable because of him. That actually sounds like he wants to make you happy