Consult a family law attorney in Idaho the laws change from state to state
My name is Stephen R. Cohen and have practiced 39+ yrs. I can be reached at 213-819-1171. I practicein Los Angeles and Orange County, CA. I give only appointments over the phone., these services do not create an attorney client relationship. My answers may offend as I do not believe in pulling punches or sugar coating the truth, I use common sense as well as the law. Other state's laws may differ and I would appreciate it if you feel like marking my answers helpful or best. There are a lot of really good attorneys on this site, I will do limited appearances which are court documents , less expensive.
In Idaho judgments expire in five years unless renewed. It appears from your description that it is child support arrearages (and not current support) that is being collected. During the time you were incarcerated your child support obligation could have been suspended if you had filed such a motion t the time, but now it is too late.
The result in your case is indeed harsh, but may well be fully in compliance with Idaho law.
Best wishes for an outcome you can accept, and please remember to designate a best answer.
This answer is offered as a public service for general information only and may not be relied upon as legal advice.