Thank you for your question. I look forward to working with you to provide you the information you are seeking for educational purposes.
The court does not represent your rights and your son's rights technically I am afraid. The issue between your husband and ex wife is between them legally. You would not have standing and if your husband entered into an agreement, legally your consent was not necessary I am afraid. As far as support, that is governed by the state's child support guidelines
and it is based on his income and the ex spouse's income, not your income.
This is a frequent source of frustration and contention by current spouses when these divorce
cases are going on. Unfortunately, the current spouse does not have legal standing to intervene, it is a personal issue you need to work out with your husband for signing the agreement if it was to provide more than the state child support guidelines provided for, but the court is not at fault in this matter as the matter did not legally involve you or your son and it was up to your husband to negotiate to try to protect you in the settlement agreement by arguing to try to pay less. It was up to your husband to argue for any consideration in reduction of those guideline amounts based on having another dependent child to care for. If your husband did not do that, then it is something I am afraid you have to work out with your husband to try to resolve.
To see if your husband signed a proper agreement in accordance with the child support guidelines, you can review those guidelines at http://www.judiciary.state.nj.us/csguide/
Also, here is a calculator for you to use: http://quickguide.njchildsupport.org/