Opinions wanted on Towing

80% range is useful for those not willing or able to do the REAL numbers but it appears you don't have that problem. Using 80% of capacity just allows you to do estimates instead of real numbers. You should be good to go but do watch your tongue weight (fully loaded, not the brochure numbers which are meaningless). With many half ton trucks the tongue weight is the limiting factor as the available payload is often reached long before the maximum trailer weight is achieved. Your door panel should give you the total payload your truck has (based on a completely empty truck). YOu have already factored in passengers, driver, cargo so all you need is the actual tongue weight. On my Rockwood this is 15% of the trailers GVWR or 1,200 lb. With a standard duty truck this MAY put you close to your limit so watch that number. Other than that you should have no problems and that ALSO may not be a problem for you.
Good luck / Skip