He sounds like a lousy father. I'd say you can either convince him that he doesn't want to be a dad and take off with your son somewhere away from him and raise him yourself. You also may have some legal avenues, please start taking notes!! write down the dates and times of events. So get a sheet of paper and start recording, write down what day and time he called your son those names and the exact words. The more info the better. That is verbal abuse so it's something against him. You have a duty to protect your son! I have experience in child/legal matters, some dads with major issues severely damage and even kill their children. If not physically then emotionally. This is beyond abuse of you, this is a safety issue for your son, and he can potentially screw up your son emotionally as well and could affect his life choices and happiness further down the line.
Your ex sucks, you need a plan. Seek out some free legal advice and weigh your options