You say good bye. You don't lay blame, you really do not need a reason other than the relationship is not working for you. But you have to be prepared that he may say anything to keep you on the hook, including suicidal ideation. He is not yours to fix.
Then you sit back and think about yourself, and what you have learned from this, and formulate what the meaning of a true partner or even a friend is to you. And then you stick with people who are uplifting and loving in ways that you want to treated, instead of hanging on to someone who does not seem to have your best interests at heart.
You said it all when you said if he didn't have PTSD you would not have put up with his nonsense. Not all PTSD folks put out his kind of nonsense, and they are quite capable of normal relationships, albeit more difficult at times than the national average.