Yes, it's often tough breaking up with someone but you do 'want out' and so that's the decision you should go ahead and make for yourself. He's not emotionally stable unfortunately, angry and mistrustful of you, which will only continue to wear you down, Noms100. As you say, he's not interested in getting help so I can't see how anything will improve.

My advice is to, yes, break up with him. And if you fear that he might get angry and abusive then I don't see anything wrong with breaking up with him over the phone. If he handles that okay maybe you can see him one last time to say goodbye in person, if that's what you'd like.