[-Skeme-]

Tricky situation. To be honest, I don't think beating him down with another guy is the answer. If he's a mean piece of [censored] like you described him, he'll want revenge on you for jumping him with a friend. It's not going to help the lady out, and it might even make her mad, if she's still brainwashed and feels for the idiot. I think you should press charges and have him put in jail for as long as possible, sue for any damages you can, and get her therapy. Both physical and emotional. You don't need this dipshit coming after either you, your friend or her. Let it go and hope he gets jail time.