funding a college education for 3 children would cost him a fortune at good schools. from a purely logical economic standpoint he should be thanking you.
i would also bring up the fact that there is zero funding in the child support account, hell i would take out an ad in the NY times ( silly). i would say it to him, his parents, his feminist friends, his employer and his housekeeper...but that is just me. your talk of this brings up many old issues from my own tug of war in divorce.
as the kids get older it gets easier to deal, they will make many decisions for themselves, and if he wants to keep a relationship with them, he'll have to act like a human.
sadly, my daughters father died in his bed at age 54 found by his mama, alcohol exacerbated his health and cold little heart, he left a huge financial mess for his only child to clean up....they were not speaking for 2 years before he died but she has since forgiven him.
hope you have an uneventful day.