If you are both in agreement that he (or you) provide more food/clothing/camps/school fees/medical care, that should be enough to satisfy the school. They don’t want both parents claiming they supply more. For FAFSA, you could also just have the children stay one more overnight per year with the claiming parent, and then there is not an issue of supplying slightly more, the test becomes time. You may think it is silly to keep a calendar, but that’s the easiest way.