Sarah, the fact is there are abusers with ptsd, and abusers without ptsd. Both, however, are abusers.
It makes me angry that you are willing to continue to pursue a relationship with this person, to your detriment. I want to show you my past, and all the people I couldn't change or save, some of whom are doing quite well at this point - without my help. I just didn't matter to them, but each of them broke my heart in one way or another.
As a survivor, it takes me a long time to form any trust in new people. My husband, who is not a sufferer, and I were friends for two years before we started dating, and we were engaged for a year before getting married. My first marriage, however, occurred 9 weeks after the first date - and he nearly killed me over a 13 year period. My rationale for not leaving sooner? I didn't want to hurt him.
This will sound very hard-hearted, but unless this guy is actively engaged in treatment, he is a waste of your time and emotion. There is someone very nice out there, just waiting for a wonderful person like you. I wish you well.