Trailer GVWR Question

Whatever the wheels themselves add up to on that scale.

Never mind that kingpin. Trailer off bumper hitches you would be worried about what is called tongue weight. You can only put so much. Fifth wheels pretty much take that problem away.

 

King pin weight is 20-25%. It won't be 2500 lbs, it will be closer to 3500.
Axle ratings are what they loot at. A non cdl combination vehicle has a 26k lb rating combined.
Using a Ram 3500 single wheel as an example.

Truck's gross axle weight rating (GAWR) Is 6000 lbs for the front and 7000 lbs for the rear.
Assuming your trailer has 2 7k axles thats a total of 14k between them, this adds up to 27,000 lbs allowed rated weight. (Safe)

When you go over the scales, the truck or trailer can't be over weight on any axle.
Trailer tare weight 7000 lb, king pin will be about 1500 lbs when empty. The 5500 lbs left over are resting on the trailer axles.
Truck curb weight is 8000, Almost 5000 lbs on the front axle and 3000 on the rear axle. With an empty trailer your rear axle will have 4500 lbs total on it. You have 3500 lbs of payload left on the truck. A 10k load will add about 2500 lbs to king pin and 7500 lbs of the load are now resting on the trailer axles. 5500 empty trailer+7500 payload will add up to 13,000 lbs on the trailer axles.
Cargo placement will play a big part in this.
As long as all your tires have the proper weight and speed rating you are good to go.
Adjust the weight numbers according to your truck and trailer's ratings and weights.