Do not rely on published (brochure) weights to determine payload, pin, or vehicle weights. The only reliable way to determine how much payload you have is to take your truck to the scales as it will be loaded for towing, and subtract that number from the GVWR that the manufacturer provides. I think you will find that you do not have 3300 lb of pin load payload available.
With regard to reducing pin load by placing weight in the back of the trailer, when I added a 650 lb quad, a 275 lb. motorcycle, and a couple of hundred pounds of gear, tools, and dog food, I reduced my dry pin weight by only about 150 lbs. The biggest effect on pin weight is what you carry in the basement, almost all of that weight is directly on the pin.