I am rolling with Founder on the portion of this I can identify with...paying for college. I helped my son get his band scholarship (he got it primarily because of my relationship with the then band director at sTu because he stunk up the audition). Once he got in school and learned the game he took over from there (apartment movie bootlegger, cd bootlegger and he played in multiple ensembles). At one point he was getting so much money out of the music department that the head of the music department told the band director he was going to have to limit my son because he was getting more money than some of the music majors.
I filled in the gaps for him but the small loans I signed for he paid back. He purchased his own car (I helped with insurance down payment which he promptly paid back).
Equip them and turn them loose. I will be a safety net but not footing the entire bill. As a result he graduated in 4 years and was pissed he did not do it in 3.5 (he did not find out about the hours he could get during the winter break until it was too late).
The one thing you did and what he's seems to not be willing to do is help his child. I'm not saying he has to do everything or even pay for everything. It just seems to be irresponsible to not want to guide your children past their 18th birthday because you get off the hook for paying child support.