WOW your ignoring argubally the best interior and motor for what?
Gas motor for why?
Mid level trim? Thats strictly a personal preference.
Forget a gas motor, diesel will return you far better fuel economy both towing and non towing. Generally speaking 4X4 will reduce your tow capacity.
Generally speaking a new 1 ton SRW will allow you to easily tow most fivers up to around 13,000 pounds.
I think you might be missing an important point though. What happens in 6 months when you actually discover that 30 foot fiver is just too small, or its missing stuff you really want? Yup! Time to go looking for more or bigger. Of course that could also mean a different truck. IMHO if this is your plan to full time, dont limit yourselves so much. Buy the truck you like best, but make it a dually. You really need to go drive all three, (GM and Chevrolet are one) before you make your decision