Sometimes there may be a delay in receiving a reply from me as I work on creating the best solution to the question you have presented.
I want to tell you that I am very sorry to hear about this problem but glad to see you were able to raise your daughter into a functioning well adjusted adult.
Your question seems to focus primarily upon whether the judge was proper in not allowing your daughter to testify and what are your next steps.
Legally the judge did not have to allow your daughter to testify because the issue of child support arrears can not be adjusted retroactively since you were denied custody of your daughter. I know this may not make sense to you and personally I do NOT agree with the law but unless you obtained a modification of custody order, then you would be legally liable for the arrears. Please try to remember that I am only the messenger and this does NOT represent my personal view when rating my answer.
As far as what you can do at this point it is very very limited. Your time to appeal the denial of custody has passed and since you did not go back to court after the first denial of custody you are stuck with an old court order with arrears. Your best option is to seek a retroactive modification of only the child support arrears after your daughter became emancipated. This will not remove all of the arrears but can have a significant impact in the total amount owed.
New Jersey has an "anti-retroactive" child support modification statute. The
anti-retroactive child support modification statute bars the retroactive
modification of permanent child support arrears. However, the statute does not
bar the retroactive modification/reduction of child support arrears that accrue
after the child's emancipation.
Hang in there and I wish you and your daughter the best.