Your max towing of 8100# can only be achieved with essentially nothing in the truck. Even the WDH that you mention comes off that #. Any other people in the truck? Anything in the bed? Take all that weight off the 8100#. Next, it would be virtually impossible to get that 7000# "dry" trailer on the road at anything under 8000#. Are you going fill the propane tanks? Any water? Surely, you must have some pots, pans, and clothes? It all adds up incredibly quickly.
You're right on the money here.
I think most people don't realize just how much all that extra "stuff" weighs.
The dry weight on my trailer is about 4,500lbs. The GVWR is about 7,500lbs.
Fully loaded with water, propane, food, BEER!, and the endless amounts of gear you inevitably pack in there, I figure that trailer is about 7,000lbs going down the highway, with about a 700lb tongue weight.
(I actually bought a tongue weight scale the other day so I'll know exactly what it is soon)
That's not including all the gear in the box, the WDH setup, and the two of us (plus the 4-legged beasty) in the front.
Honestly, I'm probably over my GVWR some days, with much less of a trailer than the OP is talking about.
That's aside from the fact that in this ridiculous Province, vehicles are limited to a GVWR of 6614lbs before you're supposed to pay extra for a high capacity vehicle permit at the registry.