Mfg. magical MAX Tow Rating is based on 150# driver and 20# cargo with bunch of *** and 'fine print' exclusions.
Real world.......is just what you found out.
You will reach/exceed tow vehicles GVWR long before getting to that mfg. magical tow number.
My 2007 Dodge 3500 has same ratings, but loaded up we weigh 7890#
Pin weight is 2900#
Puts me over on GVWR but right at rear tire load and just under RAWR
Mfg. Max Tow rating for my truck is 16,260#
5th wheel weighs 13,875#
From what I understand NEW models mfg. numbers are suppose to be closer/standardized..........at least for 'payload' number on Yellow Sticker
How it relates to real world numbers I'm not sure