Is there any possibility that she might be mentally ill after having children? Do get her checked out if so. I advise counselling to give your marriage one last shot before calling it quits.
In a divorce, it's up to the court to decide who gets custody and who will be the main caregiver. It's a complicated process, but it has to be done if the children are suffering as a result of your toxic relationship.
http://www.fycs.org/index.cfm?GPID=25
http://www.carecorner.org.sg/cccc.html
Read more