It is not just the hitch. The hitch on my DP with a Freightliner chassis is clearly rated for 10,000lbs and Thor used to advertise that it had a 10,000lb tow rating. However, GCWR is 30,000lbs and dry curb weight is 22,000. That means that the chassis is only rated to pull 8,000lbs max with nothing in the coach. A much more realistic tow rating is 5-6,000lbs depending on what is in the coach. Freightliner told me that the limiting factor is the Allison 2100 series transmission. I would like to believe that both Freightliner and Allison are very conservative in their ratins (meaning that I might get away with pulling more) but so far have not been willing to push it.
As for the 2016 F150 weighing 5,000lbs, mine weighs 5,600. It is 4wd which is required, supercrew, 6 1/2ft bed fully loaded Lariat. I understand that the sunroof added about 100lbs and the 6 1/5ft bed probably added another 150. I do intend to use it as a toad someday but will need to watch how much other stuff gets brought along.
I would bet that your rig is like mine, the hitch is good for it, there is something else holding you back.