Child Custody

Hi. I got married couple of years before. And I am a father of 1 year old boy. My father passed away and Im the only child to my parents. From the beginning of marriage, my wife and her family used to ill treat me and my mother and treated us like a slaves. Since after my child's birth, they used him as a advantage and starts playing with my life and family. My wife rarely let my mother to take the child in her hands. She used to visits her family once in a month for a two weeks. Now I cannot able to tolerate her ill treats and bad words on me and my mom. So we left our own home without being able to tolerate her bad words and blames like we tried to kill the child and we are the one who killed my father. She and her family used to threaten me that she will file a DV case on us. Now we are not going to our house and the key is with her. She took our car too. She and her family started spreading rumors on us. So I have decided to file a divorce case. But I need my boy. He is just 1 year old. All are threatening me that I will lose my child if i file divorce case. I can never lose my child at any cost. Even she threatens me like if I file a case she will take my child to abroad and will never even let me see my child. All I need is a shared joint custody. I know I cant able to get custody till he turns 5. But since it is not mandatory, how can I get joint custody when a child is just 1 year? How can I never lose my child to his mom? How can I avoid her taking my child to abroad? She will surely turn my child against me. How can I fight against this Parental Alienation Syndrome?