you have discovered the cult of irresponsibility -- this is widespread in America.
all you can do is take the non-paying jerk to court as often as the court permits. here in FL, that is when he has made no payments for 90 days.
since it takes almost a month for the court to act, and since he pays only one month's worth when so ordered [it is a 'hardship' for him to come up with any more than that despite owning two dobermans], the mother here actually gets about three month's support each year.
that's it. nothing else will be done.
the kids stay on welfare permanently so they have health insurance, since the mom can't afford both family health coverage and food in the same month. good old low skill, dead end, job -- well, that's about all you can get in FL with just a HS diploma.