• Harassment by wife and in laws; custody of child

I married in Feb 2007. My Wife and her family members are followers of some Ram Chandra mission, and call their guru as Master. They are so much hypnotised by this ashram/ mission that wife never settled in married life. She left my home in July 2007 and stayed at her parents home for 4 months. When we tried to convince her mother/ brother to continue marriage, they threatened us with harassment case. Since our child was about to be born at that time, in the interest of child's future; we brought her back. 
She does not want to do household responsibilities, and does not feed the child properly. She even eats up chocolates/ sweets brought for child. She has high hunger disorder,, due to which she threatens us that she is not being given food. She uses foul language with my mother.. 
We do not have any physical relationship. She has now filed a police case against me for harrassing and mental torture. Her brother/ mother have advised her to stay at parents home only. She has even taken my 5 yr old child, She has no concern for child's school being stopped. Over last 5 yrs her casual approach has resulted in child being underweight and asthamatic. 
Please advise how to claim the custody of child to ensure his education/ fooding. All our family members tried to convince her but her family and ashram followers do not allow her to come back. Even the police officers requested her to think of child's future, but she did not change.
Look forward to a solution