Unilateral divorce

Dear Advocates, I am 46 yrs old Muslim lady. I am married second time to a Muslim person after my first husband died 20 yrs back. My second husband has another family and they know about thus marriage. I am his second wife and we don't have any kids from this marriage. However, I have two grown-up children from my first marriage. I am staying with these two kids in my first husband's home. All of us including his family stay in the same village in West Bengal. My second husband visited me regularly and helped me with my property handling. At the same time he abused me in many ways, alleged adultery and stops me from visiting my relatives and neighbors. He always threatens me with a warning of bad consequences. I could not do much to get rid of him due to his influence in the village. I also suffered this just to take care of children and their education. Although my kids are grown up now, my husband continued abusing me sexually. He demands more regularly from me, that I am unable to provide now. Hope you understood this. I don't like this in front my children. I tried to stop him. But he became violent in last few yrs. I am totally broken now. I want to take divorce from him but he refuges to do so and threatens me. Can I get unilateral devorce from him? How long will it take? Do I need to have a advocate and go to family Court or a Muslim marriage office is enough to get the devorce?