Protection for widow (senior citizen) from daughter in law

Dear All, Need your advise as My mother (widow) is being ill treated, humiliated by daughter in law since she got married to my elder brother, who is handicapped but working with a renowned IT company and draws a decent salary. Since the early days of marriage, my brother's wife started creating a lot of conflict inside the family and her sole intention seemed to break down all family bonds between by Father and my uncle who stayed in the same house sharing two different floors. She is kind of eccentric and had attacked my mother grand mother and even went to an extent of setting fire to the kitchen to blow up the house. She uses very foul languages beyond imagination and slowly has stopped all our relatives from coming to our house, by force and through abuses. Post my brothers marriage I got married in an year started to stay separately in a rented accommodation in the alibi of work, which was actually to find some peace. Post my dad passed away, rather than being compassionate my brother's wife, stopped all financial support to my mother and my brother could not do anything being handicapped and as all his financial transactions were controlled by his wife. I have been taking care of my mother, Grandmother completely since last 2 years, however the torturing is still continuing. There has been quite a number of physical assault and mental harassment is a daily routine. She even ill treats my brother and refuses to assist him to the bathroom while denying to keep any nurse or assistance in the fear of loosing her importance, as financial control is completely with her. Recently my wife was also harassed thoroughly, when she went to stay for a week to give company to my mother and since then has not been able to go back in the fear of a conflict. Major highlight: 1> My brother though working is handicapped and condition is deteriorating (now in compete wheel chair. 2> They got a daughter which has been a major advantage of his wife as she knows he cannot think of a divorce. 3> My Brother's wife keeps threatening that she will go to the police and even attempted few times, which was stopped by neighbors by begging.4> I work outside the country and I fear that any strong objection from my end can lead into a false police case under domestic violence, which will impact my travel back to the work place which is essential, as I am the only support to my Mother and Grand mother and to my family. She has taken over the car, major portion of the floor and has tactfully even created joint account with the little saving, my dad had made for my mother. Her intention seems clear, to take over everything, trying to create a security for only herself and probably her daughter. I am also now stopped from calling my brother, kindly advise what should I do to save my family (My mother, brother and all). What can be an advisable solution here.