Mental, emotional, sometime physical abuse..what would you do ?

If your dad mentally, and emotionally abused you, your mom and your brothers/sisters on a daily basis, what would you do? And even sometimes physically but not to the point of leaving bruises so there's no proof if you were to call the law. But your mom won't make him leave. She let him come back after he moved out for a month bc they were supposed to get divorced. And during this month he was runnin around with some other chick. Who happened to be his "high school sweetheart." And he was and has been in love with her. But when plans didn't work out, he wanted to come back home and "work on his family." So what would you do?