My comments:

1. Find out what your state mandates for divorced couples with kid in terms of support

2. Follow the state guidelines on paper before you approach exh or the courts

at least you will then know exactly what you ought to be getting / are legally entitled to

3. figure out what you're currently spending (or what you spent in 2021) vs what you've received in support from exh. Calculate the delta.

Now you have two data points:
a. what you are entitled to
b. what you actually spent/received and the difference

Negotiate from the higher of the two. You can always come down; you cannot go up once you start.

M 20+ T25+
S ~15.5 (BD)
BD 4/6/15
D 12/23/16

"Someone I loved once gave me
A box full of darkness.
It took me years to understand,
That this too, was a gift."
~ Mary Oliver