That's some awesome mileage. Best I've seen out of our 05 has been 20.5, doing a day-trip with my buddy.
I too can't seem to keep it under 63-ish on the 2 lanes and 78-80 on the freeway. In MN they won't usually ticket you for 80 on the interstate (limit 70). Towing depends on the load and trailer, and mileage doesn't really matter, lol.