Domestic abuse to Mother and suicide threatening from father .

Respected Sir/Madam, We are facing domestic abuse issue in my family. To give you a back ground, we are a family of 4 My father, Mother, Brother and I. My brother is a mentally challenged kid. My father is an alcoholic and he does a lot of domestic abuse to my mother, This has reached physical abuse as well at times. He wanted to buy a new house after selling the old one. I refused to do it, the violence in my house increased. He said that I will have to buy a house with him. Since my brother is a special child, it becomes very difficult for me to move out of house. So I thought if I buy this house things will better in my family. So I went ahead and bought the house. It has been 2 months we moved in and the abuse has become worst. I want to sell the house. My father is threatening of suicide and writing our name in the note. He is also threatening me that he will hand me to cops for stealing his money. Please advise. I am really confused