Towing MPG

I own and triple tow with a 2016 F150 3.5L Ecoboost. Truck is rated to haul 11,000 pounds off the bumper and 12,000 pounds with a 5th wheel. My total vehicle weight rating is 6,900 pounds with a 2078 pounds payload. Supercab with 6.5' box. I tow a 5th wheel with a max weight rating of 7,000 pounds. Empty is at 6,000 pounds. Behind that I tow a 16' deep-v aluminum boat and stainless steel roller trailer which weighs 2,300 pounds fully loaded. My combined trailer max load is 9,300 pounds. truck weighs 5,400 pounds fully loaded with me, the wife, dogs, fuel and all the gadgets. That leave 1,500 pounds available for pin weight. I drive 60 mph and my engine runs at about 1,700 rpms. My fuel mileage is 9-11mpg depending on head winds. If I slow down to 55mph I average 11-12mpg. The F150 also serves as my daily driver and I average 19-20pmg around town and 24.4mpg on the interstate. When I tow only the boat I average 17-18mpg on the interstate. Those are real numbers.
One thing that hasn't been mentioned is the cost of repairs. Older vehicles will start to nickel and dime you to death. Sure it's paid for, but I would get tired of it being broke all the time and spend time fixing it instead of camping.