Too bad that "agreement" you had with her while she was in NY was NOT ALSO formalized through a NY court. That's where you set yourself up for this.
If anyone else reading this on the board is in a situation similar to yours, they are also at risk for getting shafted like this by an out of state agency when a parent moves with the child and NO binding court order was already in place to set your support obligation AND prevent this crap. The lesson? Getting a court paternity/support order CAN PROTECT YOU.
I'm NOT an expert here but I'd bet Mom would still be getting $530/mo from NC even if you'd had a NY formal obligation for $300/mo before she moved, so NC would have to eat the difference, and the NY court would assert it had continuing jurisdiction for whatever fusses came up later.
And now, with her applying for assistance or whatever in NC to trigger this mess, you MIGHT be stuck having to do something with courts and/or govt. administrative agencies in NC instead of NY. That's sure not as convenient as taking care of this before she moved, is it?
You still should talk with someone who practices dom rel in your area. AND MAYBE if she is cooperative, a stipulated court paternity action order between you and her in NY or NC would pull rank on the NC agency's calculations and not cost very much. Even if that costs you $1500, you'd make that up in half a year in monthly savings.
Meanwhile, if she drops whatever form of state assistance or benefits she must be getting, then the state agency involved now probably drops out of the picture. That hearing you had must have been before an agency rather than before a REAL court, as the whole notion of "let's prevent a party from attending his own case" sounds like an agency sticking it to "Mr. Out of Towner," for a royal screwing. Did you talk with an atty while you were down there? How long ago was that hearing? Can someone argue there's been a significant change in circumstances since then to facilitate a motion to modify?
A good dom rel atty may also bring up with a court the notion of if YOU are paying BIG support $$ every month, then maybe YOU should get the TAX DEDUCTION every other year. What about when you are done with school and making real money? To whom will that deduction be worth more then?
And if that was likely a state support agency hearing, I'll bet you don't even have a formal, ENFORCEABLE visitation schedule. What if you get a new squeeze and Mom doesn't approve and thus cuts you off from visitiation? Like that NEVER happens?
Maybe a court can somewhat start from scratch on support and visitation. But file this mess under the heading of "...and you thought attorneys were expensive."