Harassment by Step Daughter and her Husband

Hi, I am a 65 year old man being harassed by my step daughter and her husband. This is my 2nd marriage. My wife has a daughter from her first marriage. We got married 23 years ago. I took up the responsibility of my step daughter and provided her with quality education and a good life. She fell in love with her husband and we got them married 5 years ago. I had perfectly cordial relations with my step daughter till then. Just to clarify, my wife and I have had a happy marriage till date and have no biological children together. I live with my wife and my 85 year old mother. Also my son in law and daughter have a 2 year old child. At the time of marriage, my son in law had asked for dowry, which I gave him. He assured me this was a ritual in their family and a one time thing. Ever since their marriage, he always sent my daughter to our house asking for money at regular intervals. If I refused, she would come back next day all beaten up or he would threaten divorce. We would give in out of sympathy. Earlier this year, my son in law and daughter came to my house. He created a scene and was stubborn on a divorce. He asked for a few lac rupees to end the marriage. I asked them both to sign on the divorce papers and only then would I give them any money. I told them this is the last of any money I would give them. All this while, my daughter always portrayed herself as a victim. The next day, they came to my house and my daughter alleged that she had given me money over the years 'in cash' at '10% interest per month' which today amounts to 'X crores' and now she wants it back. I was left aghast, as I have never taken a single rupee from them. I took them to the local police station and asked them to register a case against me. The inspector called their bluff and warned them not to harass me. A few days later, my daughter and 3 of her in laws came home. They pulled me by the collar, threatened me and broke my phone. They, my daughter included, threw stones and broke all the glass windows. (I stay on the ground floor). All this was captured in the cameras installed outside the house. I can't imagine the trauma my 85 year old mother would have felt. I called for the police, who registered a NC. The police warned my daughter not to enter the building. Despite the police warning, she repeated comes home saying that it is her right to meet her mother. She sends threatening and abusive messages to me and my extended family. A few days back, my daughter went to my office, all beaten up, along with her husband, and claimed to my employees that I had beaten her up because I owe her X crore rupees. She threatened them to stop working and shut down all operations. Again a NC was registered. My daughter has become accustomed to being beaten up and can falsely accuse me or my extended family for it. I want this harassment to end but don't want the police to arrest my daughter. Plz advice