What we should do,if our father mentally tortures our mother? He becomes a gentle man outside in the society,and than abuses,tonts and much more,for each and every second that he stays in the house.
You must stay out of their business and let your mother handle it. You as his child must be tolerant, obedient and dutiful to both of your parents while anticipating your reward from Allah alone. You can remind him about Allah and advise him when he is in a good mood.