Are there any food storage boxes to use at the campground

Yes closed. And I don't remember any food boxes

I know they are on limited amenities after October 15th. This is the link for NR campgrounds. https://www.nps.gov/grca/planyourvisit/cg-nr.htm#CP_JUMP_1954293 I think Jacob's Creek may have availability a bit outside the park entrance though.

Yes. The north rim is closed for the winter...