Married filing seperate, does spouse count in family size?

I moved off Save a few month ago to IDR. My income is low and I have 3 kids. I plan to file separate from spouse so their income isn’t applied to my income. When recertifying for IDR would I count my spouse or not in family size?

Also, when filing tax does it matter if the children are on his return or mine? The accountants say the children should go on spouses return as higher income.

Thanks