I think you are estimating very well. If all you want to do is get there, and are taking Interstate highways, you could reasonably drive about 500 miles a day. That's going to be 10 to 12 hours on the road if you can handle that. Make sure you take a break every few hours.As I plan the drive, I am guessing that 300 miles a day is about 6 hours.
Is that reasonable for 1 person to drive in a day?
Am I over/under estimating 50mph, (with a 26 ft truck towing a car)?
Request a diesel if you can, you will save on fuel costs. Diesel is about the same price as gas right now, and a diesel will get considerably better fuel mileage. My son in law has rented Penskes several times to make long moves, he tells me the diesels get about 10 mpg loaded and the gas trucks get 6 to 8.
I'd recommend low to mid range chain hotels at Interstate exits away from large cities. You will have the best of all worlds that way - examples are Motel 6, Super 8, and Rodeway. They are generally very easy to access and should have a back lot or double spaces for parking long rigs.