OP went through mediation.
The ex didn't like how things were going in mediation, so it went to the court.
The current order is based on that. OP wants to sue out at the ex and the mediator - so the ex was correct to conclude that she was in a no win situation in mediation.
OP was represented by legal counsel; OP was not pro se. OP also wanted to stiff his previous lawyer when the lawyer became sick and was unable to continue representing him.
The fact that this is not a mediated agreement, but one determined by the courts means that there is a legal basis, and state guidelines were applied. Should OP wish for a downward modification, he has to prove a change of circumstance. If there has been no change of circumstance, then any petition for child support modification is a waste of the court's time.
OP needs therapy (there is a lot of anger here).