I would take the truck to a scale, loaded and ready to camp, and see what your weights really are. You're doing a lot of guessing and there's no sense or worrying over guesses.
The first part of your post where you state that the rig handles fine all over the country would tell me that I would continue to just enjoy towing as you have been. I would make certain that you aren't over tire weights. If you are I would upgrade tires when you need new ones anyway.
Even if you were 350 pounds over, that's basically nothing. I wouldn't sweat it. I'm one of these "crazy" guys with a truck camper. I travel all over the country loaded about 2,000 pounds over my GVWR.