My question involves child support in the State of: Georgia

My husband is active duty in the Army. He received physical custody of his 2 children during his divorce three years ago. She was ordered to pay 75 dollars a month child support until she was able to find a job and was then supposed to report how much she was making for the amount to be adjusted. She has been working the whole time and never reported her income and has only made one payment of 75 dollars in the 3 years. He is deploying soon and his exwife took him to court and was awarded temporary custody while he is gone. We are upset because the children are very obviously better off here with me, but I have no rights to them no matter how bad of a parent she is. Now it looks to us like he is going to have to pay her an insane amount of child support while he is gone. (We are waiting to find out for sure how much) What are our rights here? It is not fair that we have taken care of the children with no help from her and now we are expected to provide her almost half of my husband's pay.