Can an email discussion be sufficient update for child support?

My ex husband and I have had a child support order from when we first separated in 2011 in the state of NC. As time went on, and 3 years went by (in the state of NC it can be updated every 3 years), he stated he wasn't able to increase child support. I felt sorry for him and suggested that once our daughter started elementary school, a public school, and we didn't have to pay for the expensive daycare, he could maintain the current monthly payment to make up for the lack of increase in child support.

Our daughter started kindergarten this August, and last month he stated child support needs to be adjusted due to the fact I won't be paying for child care anymore.

Because he's such a difficult person to work with and me not wanting a negative atmosphere for my daughter, I gave in and provided my income tax return and used the online NC child support calculator filled out with my income, and the salary he stated he makes. He never provided an income tax return, and stated he can give me a letter from HR stating he makes this much per year, and sent a copy of his last pay stub. I told him there was no need as that proves nothing and that if he wanted to show how much he made, he should provide the income tax return, just like I did.

For the month of August, he only sent in the "new" amount. Last week I emailed him and stated I do not think it's fair that he did not keep his word, and asked him that if he wants to decrease the amount of child support, he should do so in a legal manner and provide all the required documentation. Today, he only sent in the new amount again...never responded to my request. When I asked him if he received the email with the topic of child support, he says he doesn't have access to his emails at work. This was days ago and he can check his emails at home, on his phone, etc. He chose to ignore it.

Is that online form I sent to him with the numbers he gave me, but that I typed in and forwarded on to him, enough to update a child support order?

I don't want to spend thousands on an attorney only to hear that I screwed up by filling it out (no signatures were on it, it was simply an email where I stated that that's the new amount taking his word on the income he makes).

The original child custody order from 2011 has erroneously low costs for child care and insurance (which I pay). I am pretty certain there's nothing I can do about that now. But I feel pretty taken advantage of and have reached the point of such resentment towards him and I want the numbers to be what they should be, and update it every 3 years regardless from this point on.

Thank you for your feedback