Child Support Hearing

Location: New Hampshire

My ex-husband and I have a court order that states he is to pay $1300 a month in child support for our children. About two years ago he messaged me saying he was only going to pay $700 because he thought that’s what was fair. He then began telling me that he would get lawyers involved and go to court for custody if I didn’t agree to the change, and that he would withhold all support until we went to court. In a text thread I essentially agreed to accept $900 a month. I was not going to have to deal with fighting for my children over money.
During the last two years he has not paid anything when he has had them for his 30 days in the summer because “his lawyer told him he didn’t have to” and would withhold the support when he was upset about things. Him not paying support during the 30 days a year he has them is not written in our court order. We have a hearing coming up to discuss the $10,000 in arrears. He claims that the “agreement” we have through text means that he shouldn’t owe it. The children and I live in NH and I have no idea if it’s worth pursuing this hearing, or should I just ask family court to drop it? He has never gone to the court to have the $1300 changed to $900. All he has is those few text messages.

There are also text messages and phone calls where I explain that I was not agreeing to the change, and that he bullied me into a corner by threatening me with lawyers and court cases.

I guess I’m wondering if he has a valid argument and if I should bring a lawyer with me to this hearing.