It seems to me that he feels he is trapped by his family; if he cannot change the family and the family doesn't comply to his wishes, then the only way is to harm himself and revenge.
The good thing is that he is still talking to you. Try to use this leverage from time to time. I hope you all find a way to solve this with no one trying to control anyone. Controlling others is harmful, and it seems central to this challenge.
Also, is it an option for him to start his life somewhere else not close? I know parents like their children to be close to them, but sometimes, it's better if they are not if they cannot get along. I know it's better for me and for my father to be away from each others. We simply cannot get along because he wants me to be someone who is not me.