I wouldn't waste any time thinking that his mental health issues are the cause of his abusiveness. He's abusive and he has mental health issues. They are separate issues.

Don't worry about him. He will be fine. It sounds like he has family. Worry about yourself and keeping yourself away from him. It might be a good idea to block him on social media and change your phone number, if you haven't done that already. You will be tempted to think he is going to change and want to go back to him. Do whatever it takes to avoid that.