How to deal with matrimonial issue?

Our marriage took place at her brother-in-law's place. We have been told that her ex-husband may harm both of us, and there is a life threat. They didn't even show me my wife's parental home due to the same concern. During the marriage, they didn't invite anyone from their family and asked me to get our marriage registered. However, her brother-in-law started pressuring me aggressively to register the marriage, which raised doubts in my mind, so I paused the decision. My wife told me her brother-in-law is dangerous and that she would never speak to him, but I later found out that she was in touch with him. When I asked her about it, she shouted at me and called her brother-in-law to inform him about our conversation. A few days later, she went to her parental home and switched off her phone. When I visited her home, her brother-in-law abused me and my mother and said that without registration, the marriage doesn’t count. She was present during this but said nothing.