Who Gets Custody in a Divorce

My question involves a child custody case from the State of: Georgia. The father and mother have separated with the father having physical custody of the child. The mother moved to another state and filed for custody there. Prior to the separation she threatened that the father will never see his child if he left her. He has a parenting plan and wishes only to be a good father. He will maintain insurance and care for the child, she will have liberal visitation rights. What should his initial steps be? :confused:

First, she needs to have established residency there to file for divorce. Dad should file for custody and child support as the children are subject to the jurisdiction they live in. If mom has not established legal residency in her new state, her filing is meaningless and dad should also file for divorce at the same time.