Should I forgive my father?

I’ve had to learn how to deal with a lot growing up. My parents slept in seperate rooms for 11 years. Their relationship went to hell when I was 9 years old. I am now 20 and in my third year of college and I can’t help but hate my father. My mother does not have very much self confidence, yet she is a beautiful woman. It is his fault. Disturbingly at the age of 12 my mom started to tell me about their personal life. He told her that she was boring in bed etc. She would cry and I would hold her and make her feel better. I stayed with her to make sure that she wasn’t lonely. My dad ignored myself and my brother growing up and repeatedly cheated on my mother with several women. He would come home at 2-3am in the morning and most of the time left before six a.m. He was gone every weekend. This year my family was sued for 4.2 million dollars, now my father is leaving my mom for his secretary. The had been having an affair since I was 8 years old. Should I forgive him? If so, how?