GVWR times 25%........wet pin weight
Can truck handle that with available real payload?
YES.......buy the TH
NO........don't buy that TH OR buy TH and get bigger truck
This is not rocket science just adding/subtracting/multiplying---simple basic math
OP is making it more complicated then necessary BUT when all said and done should have good towing combo.
Dealer allowing prospective buyer to load up unpurchased TH with cargo, stuff, water, fuel in order to get weight is something I hope OP videos cause that is not happening. And without fully loading weighing is still just a 'guesstimate'
Best wishes to OP.
I'm done.