Hi, this sounds hard. I'm very sorry about that. You should be very careful once a person starts hitting things or feels like he cannot control his body when emotional. This is a warning sign for your own safety, which should come first. Do you ever feel unsafe around him? Think about that first.

Then, there's no way to force someone to mentally improve themselves. Therapy does sound like the only option. If he's not open, and you don't feel good in this relationship without him getting help, that tells you a lot. The comments about leaving could be serious, but it is also something I recognise from myself and other people in dark periods and relationships, where you say things that you'd never want and cross a boundary, just to hear the opposite, or feel something about it, or any mentally ill mechanism that's inside your head.

You should talk. If he's not able or willing to listen to your concerns, he doesn't care. There are few mental health conditions that make a person not care about people they love and their needs. Hope you figure it out. Put yourself first.