Indiana is 21, too. My step-daughter quit school, worked part of the time, moved in and out of her mothers, didn't enroll for college, etc. Her mother was having her move in when we were going to court and then throw her out later. And she would try saying she was going to college but never signed her up.
We filed a motion pro se but ended up hiring an attorney. We had to prove certain things like 18, had not been in school for four months or more, is or is capable of working. We had one judge say we had to prove she was paying for insurance, rent, etc. before he would emancipate her. We finally changed judges because another read the law different.
Look up NY's child support guidelines and look for emancipation. Look up or call your county office in charge of child support and ask about filing pro se.
Good Luck,
Gearhart7