Dad issues

I've been fighting with my dad for a long time. Since I've was little until now and since my parents got divorced he's gotten crazier. He and his family tell me horrible things about my mom, and would make me feel horrible about myself by calling me fat. Now I'm older I'm made the choice to stop seeing him. I'm glad I stood by this choice because he has now said that and I quote " you will no longer get anything from me, you no longer have a father". Now I'm fine with this I really am, I wouldn't see him any ways but, my question is what should I call him, dad or his first name?