I run 89 Octane in the summer as I get about 15% better mileage in hot weather. In cooler to cold weather, the 87 octane provides the same mileage as the 89 so I burn 87. Lots of advice on aero, and they are correect. Running with no trailer and scale weighed at 9,800 pounds, 2021 Ram with 6.4 and 3.73s, did a test run a few days ago. Reset the Evic each time we changed the primary direction of travel, heading east 40 mph wind out of the SW hitting on right rear corner, 19 mpg, turned south Wind now hitting right front corner and strong enough to move you around in the lane when it gusted, 14.8 mpg, then headed south SE, wind almost directly on the tailgate, 22 mpg.
Towing the kind of weight you are, minimising the impact of pushing through the air is going to give you far and away your best bang for the buck. Keeping your revs in the lower range while cruising will also help, cruise control works well for that as long as you takeover with manual food feed in hills. I would also experiment with tow versus non-tow. I know on flat ground non-tow gives me a lot better mileage. Best of luck, hope the patch comes back soon for you.