father's father

What am I supposed to do with my father? I am so debilatated by all of this pain and I don't know what to do with it. How do I deal with him, how do I talk to him, when I hate him so much, when so obviously just wants to use me to get back at my mom or whatever. I can't see anything real in him whatsoever. So what do I do, and how am I supposed to feel about it? Can I just sever him or something? Is that really possible? What about just writing letters for the rest of my life? How can I take him seriously, see him without a mask of stupidity when I have to see him doped up on coke every week and a half? Who is this person, and why is he my responsibility?