If you go with the manufacturers numbers you will be allright.
My RAM when hitched up with 3,500 # of pin weight the left front wheel has 2,850 pounds on it. At 80 psi the tire is rated at 3,085. So I only have about 235 pounds of leeway.
The rear wheels when hitched with 3,500 pounds of pin weight come in at 7,350, with the passenger side being 3,750. The tires when inflated to 65 psi and running as a dual wheel are rated at 4,940 pounds per set.
So taking that inflation rating I have about 1,210 pounds leeway on each dual or a combined leeway of about 2,400 pounds.
One thing worth noting is if you plan to adjust pressures differently than the recommended inflation rate you will need to weigh everything to know what you can safely inflate to. You mentioned a whole lot of weight, do you know how much weight?
Hope this clears up the weight on the tires dilemma.
Peace
Dave