He owes you $3000, you say. Guidelines say you owe him $260 monthly for 3 years =$ 9,360, and by % reduce the 3K by 20% to $2400. Balance you owe is $7,000 and his support gets reduced. I say you you go to court and get it modified to what is actually fair and best for your son since you are making more money and only have expenses 50% of the time. You can trade the $7,000 for paying the attorney fees. Judge can't vary the guidelines more than 5% without extraordinary circumstances. Miscalculations on the guidelines worksheet are straightforward basis for motion/modification, I'm surprised he hasn't filed yet he has an easy case.

I sense you're anger at the lack of true justice but it's a wash, IMO any "victory" would be hollow. There is no mommy card to play as it's just about numbers and you've singed off on everything else. CS is always modifiable.

You were obviously decent and level headed enough at one time to agree to shared custody and avoid a destructive court battle, you may have to swallow hard and do it again. and again.

It's a lot better than what I have to live with.