I do know of one person in my family who was able to get his support order reduced when he produced receipts showing the "support" he was giving his children. He had to repeatedly ask for a hearing in front of a judge. His lawyer told him it would be a waste of time. He insisted. The judge finally set the hearing and asked him "sir, why don't you want to support your kids?" "He said, Your Honor I DO support my kids," and he produced his receipts. The receipts he had included medical, dental and vision expenses. I'm not sure if he went further showing receipts for shoes, clothing, school supplies etc, but probably. He kept everything.
You can always try to present your "evidence" to a judge, but no one can say for sure what a judge will rule.