Im in the same situation , looking into a new truck . Most of our miles will be non towing. My 2500 6.0 gasser with 4.10 gears 4 spd gets 8 mpg towing 6000# and approx. 13 mpg around town solo.
A 1500 as described will do the job. Pay attention when you load up the truck with your stuff. Keep an eye on the tire ratings, you might need to upgrade the tires weight rating. BTW, the wheels have ratings too.
My personal experience is the smaller fuel tanks in gas engine trucks. I prefer longer range between fuel stops because refueling with a TT can sometimes be a pain getting into tight stations.
The diesel set up allows using an in-bed fuel tank without a pump. As per a call to Transfer Flow , new Fed. D.O.T regulations do not allow gravity flow anymore for gasoline aux tanks.
I'm going to look into the baby diesels in the 1500 series. I have no idea if this is a good idea or not. I know of a Pilates instructor that drives one but I don't know if they are compatible with yoga or not.