Maybell, my H is not nearly the slacker in the parenting department that your H is turning out to be. Still, I'm finding that there a limit to his sharing percentage. During this most recent round of calendar shifting, more than once I offered him a "make-up" day for a day he said he couldn't do. He consistently declined. I have tracked his overnights since Day 1 of our S, and he's settling in at 33%. (Only overnights count in FL.) That's the best he can do. And I'll have evidence of that when it comes time to make it all legal. I hope you are doing the same. You can't make him take the kids, but you can make him pay instead.
