My father is having an extra marital affairs with another woman..he has been ignoring my mother and

My father is having an extra marital affairs with another woman..he has been ignoring my mother and me since many years..he doesn't even provide any share of his income to my mother..he has openly said us that yes he has an affair and would not give any single penny to my mother..and also he will be living with the another women without marrying..he is working in CRPF as sub inspector..and he is also threatening us that if we approach court than he will kill us and will file a fake complaint against us for domestic violence...what can I do in this case..how can I stop my father illicit activities and give justice to my mother..I don't have any solid proof against him..he has money and muscle power but we don't...also I m 28 years old..my father is 52 years