We've owned 3 Suburbans over the years, a GMC Safari van, and a mid-size SUV (Trailblazer). The PU in my sig is the first PU we've ever owned. I'm asking my self now why did I wait so long?! We love it. My wife is short also, which is in part why we don't have a cap. She couldn't reach the window/hatch when it was open. We sold it and got a Extang Solid fold cover. We keep a cargo bar near the back and use it like a trunk in day to day driving (similar to APT's board). Unless you live 100 miles from Costco, we've never had problems with groceries. The back seats on crew Cab trucks also fold up for hauling things inside the truck cab. For smaller things when camping we can put them in the back and they are secure and no one sees what's back there. If you have something that you don't want damaged, you secure it with bungee cords or a ratcheting tie strap. The cover we have is removable to carry bikes or other large loads.
PU vs SUV. PU generally has a higher payload and higher overall capacities. SUV has more seating. Pick what's best for you. I will never go back to an SUV. A PU is cheaper than a similarly equipped SUV, gets about the same if not better mileage, and is far more versatile. Though the latter is dependent on how you use it.
1110# payload on truck? Seems very low for a newer truck. That's the kind of payload you'll see in most SUVs because they are heavier to begin with. Our 1/2 ton PU has over 1600# of payload.
Mileage will be worse. But probably not as bad as you think. I know the Ecoboost does pretty good, but with our Sierra we're getting 15-16 in city driving and 20 on the freeway. Towing a trailer is NOT cheap. So if you're concerned about mileage, maybe this isn't for you. When comparing it to staying in motels, its a wash. You RV because you love the life style not because you're looking to save money.
Maintaining 2 vehicles just so one is for towing may cost you as much if not more than just owning the right size truck. Insurance alone may make it a wash. Not to mention that the worst thing you can do to any vehicle is just leave it sit for long periods of time.
I'd get a 1/2 ton. That trailer can be easily towed by any late model 1/2 ton with a 5.x liter engine or larger. Some will argue that a 3/4 ton doesn't cost much more upfront, and that's true. But it's like free puppies. They aren't free for the life of the puppy. When it comes time for maintenance and repairs, the 3/4 ton will cost more. However, if you are truly planning on the Sea-Doo, then yes, you need a 3/4 ton!