NY Child Support, Questions

My ex was making much less when the original order was put in place 5 years ago. He is now self employed. He makes $30+ an hour and works well over 40 hours per week. The problem is he gets paid in cash often and has filed minimal amounts on his taxes. He claims he stays home to watch his other child so he only works part time. He still pays full daycare for her though. He keeps her home by choice. He says his gf pays all the bills. It's a crock. He says he talked to a lawyer and he will get a huge decrease because his taxes say he makes much less. What do I need to do to prove he makes more? He will say he makes $30+ an hour but only works p/t. Will the judge go off of him working 40 hours? How likely is it he will get a decrease in NY state?

He wrote us a bill for work and his hourly rate is $30 an hour. Several people he has done work for also have bills stating he charges $30 an hour. I've recorded him saying he makes $30 an hour and how most weeks he works sun up to sun down.Just recently he said he only works part time. Not sure if the recordings and such will be proof enough. Maybe getting his bank records will help.

He is also the executor of his mother's estate. She died several years ago and he manages several apartment buildings in her name. He says no money is drawn off the account for the apartments so it wont count as income. Is this true? He's cheating the system and our child. It's disgusting.