Divorce for nei

Hi, I live in Singapore and got married in 2004 nov in Delhi. My wife is from Delhi and my parents now live in Haryana.I was living in Singapore before marriage. I have twice decided to go for divorce. First time she and her family requested to give her another chance to mend her ways. Things became better but soon after she came back to her normal self i.e.,violence, no house chores, demanding material gifts etc. In fact I suffered a minor stroke in 2006 due to severe stress levels I was going through in the marriage. Second time I asked for divorce in 2014,this time her family asked to see a Counselor. We did so . Saw one in fortis gurgaon. Doctor told her what to do to make situation better and she too apologised n promised if she does not change her behaviour, she herself will go back to india. In 6 months time after coming back to Singapore, she again started behaving like she used to. Now she says I should go india n file for a divorce n she will sign the paper. But I know she won't. I have three daughters of 7 yrs n twin daughters of 5 yrs each. I want to take the custody of the my daughters. I have no idea how to go about this n what all evidences I need to prove my case. Please advice. Thanks.