PAYLOAD has NO 150 lb (or any other weight) person excluded from it. EVERYTHING including the optional equipment on the truck will reduce the payload from the VERY optomistic brochure listings. The AVAILABLE payload must handle tongue weight of anything being towed, weight of the hitch, weight of all passengers including the driver, all cargo carried in the truck. The method YOU used is absolutely foolproof and regardless of where the weight comes from your truck is limited to the GVWR listed on your door post on the DOT safety plate.
Good luck / Skip