Payload for my Ram 3500 Truck

But, the GAWR front is 4750 lbs and the GAWR rear is 9350 lbs for a total of 14,100 lbs.

Trucks working out here on the road that size can legally/safely carry weight determined by their axle/tire load ratings and in particular those big 9350 rawr numbers as their going to carry most if not all the TC weight.

Many one ton drw trucks rear axle can weigh in the (estimate) 3500 lb range leaving the truck with (estimate) 5850 lb payload in the bed. You need to weigh the trucks front and rear axles to know how much payload the truck can carry.

Vehicles (trucks and trailer) brakes at the minimum will be whatever the sum of the axle ratings are.
Example the trailer with tandem 7k axle has 14k lb of braking performance and 4750 plus 9350 = 14100 lbs will be how much braking performance your DRW truck has at a minimum.