It's a hard question. His attitude implies, to me, that he still holds a hope to get his ex back. This is a situation I know well. I have an ex I loved deeply and still love. The difference is, I've moved past it, we're friends, and if I met someone else I loved, which is something I sincerely hope to do, I would never withhold one bit of love for that new person simply because I love my ex. She's with someone who good to her and she's happy with and I'm happy for her. And I'm sure she would be happy for me if I found someone new.
Sometimes we hold on so tightly to the pain of the past that it becomes almost our identity, defines who we are. And we're afraid to let go and move on because we're frightened we'll lose ourselves. I suffered from this for a long time, believe me. The problem is, really, if we love someone from the past, someone we've lost, we don't allow ourselves the room to love ourselves, because since that person left us, we're not worth loving, and only their return can make us lovable again. And when we can't love ourselves, and see ourselves as worthy of love, we aren't capable of loving anyone else. And so we get stuck, we can't move forward, we can't move back, we can't move at all. We just become frozen. It becomes obsession rather than love. Which isn't healthy for anybody.
The problem with you staying with this guy is that his obsession devalues your worth and self love as well. Love is too precious and too hard to find to wait for this guy to realize whats right in front of his face if he isn't willing to change and resolve these issues. He deserves a chaqnce, but you deserve better.