LISTEN TO STEVE!!
That chart number is for a bare, naked Expedition, no options except max tow, no cargo, only 2 passengers at 150# each and a full fuel tank. You can easily have 500 pounds of options, which must be deducted from this number. Also deduct passenger weight and cargo weight in the truck. That number shrinks quickly.
You are better off starting with the YELLOW LABEL number. From that, subtract ALL passenger weight (no allowance in Payload), all cargo weight in the truck, 80# for WD hitch, and 10% of the GVWR. You may pull it dry, but I doubt you pull it empty. All the clothes, bedding, pots and pans, lawn chairs, and toys in the camper will push the weight way up. An empty 50 gal fresh water tank only saves 400 lbs, and only 40 lbs of tongue wt.
That Expedition is a great vehicle, but is was NOT designed to pull a heavy trailer!
Do not believe any salesman about towing capabilities. They are much more interested in making a sale than your safety. And they are usually very uneducated about towing capacities.