As I've posted about a couple times before, you definitely can't use coupons on an F&F day, the F&F 10% off gets applied to your transaction as an automatic coupon that can't be combined with other coupons. An employee who didn't realize that's how it worked had told me the day before an F&F sale a few months ago to come back on Sunday, and assured me that the other coupon I wanted to use would work with it. When it did not work, he manually adjusted the item's price down by 10% and removed the F&F coupon so that I could use my other coupon, but only because he had promised me personally to make it work that one time.
It seems like, longer ago, they used to actually have the prices on F&F day 10% lower in the system like other sales, so you could use coupons with it. But not with the way it works now.
When you say coupons, does that also apply to surprise points (AKA Freecash)? Most surprise points say they can't combine with coupons, so if the F&F 10% is a coupon, that could prevent surprise points from applying.
I can't figure out what the heck Sears is doing.