Dowry Harassment

My daughter married to a guy who started demanding dowry, in the form of a house, he demanded that the flat which l had purchased in my daughter s name should be registered in his name, when l refused to do so he abandoned my daughter ( pregnant) and never came back . At time of delivery did not take my call, four days after delivery he came home and demanded 35000/- every month to stay with his wife and son, l refused and he vanished never to return. We waited patiently for 4 years but he never responded to my emails or WhatsApp messages. Finally We approached the police station , the police tried everything to reconciliation, but the family did not respond, the boy came a couple of times and gave story and promised to take his wife and son in 6 months but he is still playing hide and seek, the police have not yet filed FIR even after one year, still they say they will try for compromise, in the meantime the boy has threatened to slit my daughter throat by hand indications, this was reported to police, yet no FIR raised even after a year and two months Please advise how to move forward