Custody of child to father

Sir I have a child of 4 yrs old. My wife uses abusive language with my mother as I dont reside in mumbai .I work in saudi arabia. She is truly irresponsible in case of upbringing of my son. My mom takes care of my son in studies.. when sick.. having food etc. She kept fighting with me along picking some silly issues. I got fed up and shifted to saudi. Now its high now I have decided totake a divorce. I am a muslim. Her relatives also r on our side. Dey r also fed up of her. She has no place to stay nd has no earning too. Father expired nd mom. Workin in dubai as maid. Since m nt I mumbai she continuously tortures mentally and uses abusive language with my mom. She also threatens my son and does not allow him to come to my mom and ther relatives. My son also is afraid of her and when she is not around he keeps tellin my mom k dadi mujhe mamma k paas nhi rehna hai. Mai daadi aur pappa k paaas rahunga .Pls suggest me so that I can take the custody of my son and look after him... pls help me out. I feel she is mentally ill. Bcos she has created scenes many a times. Pls help me sir. My sons future wl b destroyed. I want the sustody of my son.