I think you have a pretty good grasp on what he is up to. He is trying to blame you for anything that he can. And then some!
I'm trying to figure out how a joint account is going to be useful. I wouldn't think it would be good to be responsible for anything with his name on it. If you need money from him, I think you would want it in an account that only you could draw from. But having a clear plan of who is responsible for what is certainly a good idea.
For as rotten a situation as you are in, you are sounding good! Detaching helps.
