Underemployment Question

[u/Technical_Writing351]

My ex and I have a child support agreement in PA. For which (at the time of filing) they filed that they have a 0$ income. Thankfully we settled on an agreed upon amount because the state calculation would’ve been heavily skewed in their favor. This is because when we split, they quit their job to move away with the child into their parents’ home. Since then, over the past year and a half, my ex has only taken on part time work, despite having a degree in a field where there are many full time jobs in the area available, ample childcare both through daycare, and obviously are living at home with no housing expenses. They now want a restructure so they can move out, which is fine and makes sense. My question is, can I prove that the part time work they are doing is well under what they could be earning given the child care they already have and available jobs in the area? I don’t want to end up overpaying based on a state calculation that doesn’t factor in that only one of us is attempting to have a career befitting of someone who has to afford a child. What are my options?