Father expecting custody for his son and divorce

I got married 6 years back. I have one son (3.5 Yrs Old). From day one after marriage my wife use to share all information whatever happening in between us and inside our home. Her mother use to guide her for all small things and it created more issues. Whatever I advised to my wife regarding this , she will inform to her parents saying that I was torturing her. In this six years, four times she created big issues and went to her native. If I try to call her back, her father will use some bad words. Every time after 2 months or 6 months she will come with her father and he will use Death threats against me. Her father is a Police inspector. As I want my son always in my life, most of the time I controlled my self and I was adjusting a lot. Last Nov 2014, we went to my native on my Son's Birthday. I have not invited anyone including her parents. Because of this, my wife scolded my Mom & me and left my home and went with her parents along my son. Last 9 months we are not living together. My relatives called her father to sit and talk. But he is not coming to talk. My son was studying Pre KG when they left my home. Once I went to my wife's house to meet my son. but her father started beating me at his home. Also I have some evidence to prove all these incidents happened in my life. Can anyone please help me?.. Myself and my mom affected a lot because of these issues. First I want my Son with me. Second I want divorce from my wife. Thank you in advance