Good advice. Especially the part about showing him the bruises and asking him to look at what he's done, and whether he's going to beat his future wife or his kids.
I would get him where he sleeps. If you absolutely have to fight back, be ruthless and unpredictable, go for the throat, try to put your thumbs in his eyesockets, bite, yank at his hair, throw punches at soft targets - the throat, the stomach, the groin - pick up something heavy or sharp as a weapon -- or don't attack directly. Bide your time and hit him hard when he's not expecting it. There's nothing dishonourable about fighting dirty against a bully. Even 'big' men can be intimidated or put off by what they see as insane people who can be a genuine threat to their safety.
Don't even bother if you're not going to hurt him or be genuinely scary though. And be aware that violence often begets violence. Maybe you should just acknowledge he's being a grade A cunt and shop him to the police. A blood bond is as nothing anyway if this kind of shit is going on. Disown him.