Mental harrasement

Sir, i am an unmarried lady, we r two sisters and dont have parents. So i am a govt employee and elder one and 4 yrs back i got my younger sis married to a man who was wkng a civil contractor in bangalore. So for the 1st yr they were ok and had a male child and since then problems started, he came into words of his cruel mother and sister and started harrasing my sister and me to give away our property on his name stating false words that we have told him that we will give him our property. Since i am alone my relatives such as mama and chacha stood with me and did all for marriage and given 3. 5 lakhs as dowry and 120gm gold. So he took all gold and kept in bank and borrowed loan from banks secretly. His mom has asked money so he did so. And it continued and second issue was born in this year january. They compelled for abortion after 1st issue and then blamed us fo that. I quarelled with them and brought her for 2nd delivery. Every now and then husband calls all my relatives and tells that he will kill all. And he msgs me v.vulgar words. Sis is not in a position to take decision. She is mentally not fit. His parents are blaming us for evwrything. They didnt even come to see the child for these 9 mnths. And he has left jobs 3 times and joined again, he doesnt have specific mind. He accuses everybody in our relatives, and blackmails. He has a perverted mind. He calls all our family members as keeps of their husbands etc etc. Sister is mentally unstable with her children. We are scared to send her to her inlaws home. What to do pls guide me