Relational

I have a boyfriend for whom We both are fighting with our parents for our marriage. The problem is he is very aggressive and uses very abusive language. Also he is very pessimistic. He has used offensive language in front of my parents also. His mother is a divorcee and she also uses very abusive language. She is also fearing that once I gets married to him, her hold on my friend will be lost and she being handicap and being chair ridden will be thrown out. Now the problem is how to change his way of talking and his pessimistic attitude which makes him obsessive at times. Once he is high on his head he challenges me that if I leave him then he will ruin me. Please advice what to do?