Keep your wits about you, and don't let your guard down. Could be a simple domestic dispute or maybe some new type of scam. It feels suspicious, and is filled with deception.

I think vid makes the best point with doing something that will let you "sleep well". Whatever that means to you.

In your shoes I would be pissed off. Someone is trying to scam you. Either this guy, or his ex. Someone has or is dealing with your in a fraudulent manner, and I am not always a forgive and forget guy. Is this guy a Grade A psychopath? Unlikely. If he was so violent and dangerous and flying off the handle he would be in jail by now. He was pissed off and lost his temper with you. He threatened a lawyer, not a beating...and a lawyer makes no sense. He probably cools off, gets mad at his ex, and the whole thing fades away. He's mad at her, not you. But do what makes sense to you, what seems fair and consistent with your personal ethic. If it was a fair deal, it was a fair deal. If you want to try and work with the guy, work with him. Whatever lets you sleep at night.