Welcome to PsychCentral, Adhesion. I think the handwriting is on the wall, so-to-speak, if he wants to be alone and is seeing another woman and introducing her to his friends, he does not really want to be with you. It even sounds to me like he is using your slap against you, to make it more than it is so he doesn't have to feel bad about what he himself is doing to end the relationship.

You can only take care of yourself. If he is pulling away, you cannot make him come back. You can work on your life only and with him wanting not to be there, I think whether or not to forgive him is a moot point other than whatever you feel about it. He needs to be working with you to repair the relationship or it cannot be replaired.