My Father in law is abusing me & threatening to fill wrong dowry case

I got married on 7th July 2014 and we both were happy. I had a small verbal fight with my father in law, which hurt his ego and and My Father in-laws is abusing me he is using very bad words and also threatening me and my family to fill wrong dowry case. He is an employee in Indian Air Force and is ranked as Sergeant. He says with the help of Air Force Wives Welfare Association (AFWWA), he will fill the dowry case. He also took my wife and 3.5 years son to his place without letting me and my family know. My son was in playgroup but it is been 6 months he is at my in-laws place and not yet joined any school over there, They are not allowing me to talk to my son and even if i am able to convince my wife they will wash her brain my saying wrong things against me. My brother in law stayed in my house for around 1 year and i used to manage many of his daily expenses. I wanna live with my wife and son and in the mean time i also wanna fill a case against my father In law.