My daily driver right now is a 2017 GMC Denali 1500 with the 6.2L. For a truck the gas mileage is very good, I am sitting at 9.8L/100kms with 50/50 city & highway.
For towing, the engine has more than enough power for your weight. The problem is when towing a big square box, like an enclosed trailer, the wind will really push the truck and trailer around - especially in the mountains. I also find the 6.2L and the 5.3L start starving for air at high altitudes under heavy loads.
That F250 was a very wise choice. Just do oil changes more often than not and use high-end motor oil - seeing motor failures around 300k.
