You have to file with the courts, they will do the rest. Tax refunds, government checks, unemployment everything will be diverted to the child. If this still does not work they will put him in jail! Talk to the Bar Association where you live they will refer you to a low-cost or free attorney that can assist or at least lead you in the proper direction.
When My uncle couldn't pay child support and was way behind on payments he was arrested and put in Jail where he then worked to pay off all of his debt. Perhaps this is something that could happen for you, I know it motivated my uncle more to find a job even if it was something he didn't want to do, the alternative was jail.
Well if he doesn't want to work, that's ok he can enjoy life behind bars...I would still file on him, get something going..They have to make him pay.. And after it stacks up and he hasn't paid, he'll enjoy 3 meals a day behind bars.. Then maybe that will motivate him to care of his son..plus you can go back 4 years on him. Whether he works or not, so that will be added to his debt, and he will go to jail sooner. In some states they also lose drivers license...Good luck.
First thing to do is check with state you are in and if there is an intelligible person working at Health and Human Resources (what we call it in our state) is to get in contact with child support enforcement bureau or something like that to maybe get some sort of process rolling.
Call the attorney general. They can order it. It will add up each month and you can intercept his tax return until it is current
File for child support anyway and let them do with him what they wish,jail etc. Because there are other things he could do in the childs life but since he is not active in the childs life I say file for nonsupport.....the best to you