This is a hard situation to be in. It sounds to me like he wants out of this relationship, but can't find a way to leave gracefully . . . because there is no graceful way to stop loving someone.

I'm suspicious of people who decide they need to get away from their significant other, in order to work on the relationship. He says he needs a commitment from you to change before he can come back. You are who you are. Even if he came back, won't you be wondering how soon before he will go to his sister's again. I would find it hard to trust a man who seems to act like he doesn't really need you.

Try not reaching out to him. Leave the ball in his court, and see what he does. Give him A chance to miss hearing from you.