Two years ago we did a ten week, 13K mile trip back East covering much of what you plan on doing. We took our 1995 Sidekick and would not have had nearly the fun we had without it. If you have no problem with the dolly, I say go for it, you won't be sorry.
As for gas stops, we have been COSTCO members for years and my brother included us in his Sam's Club membership. There was one COSTCO station that was tight but all were doable. We didn't buy gas for the rig anywhere else so don't know about regular station other than the one on Blue Diamond near the Oasis RV Resort in Vegas and that is really tight except on the end pumps.
Our mileage suffered, but, I still take the towed and have upgraded to a 2006 Grand Vitara which is a little heavier.