Just a couple of thoughts as you continue to plan. First and foremost, if you're cutting up sites and drives into small chunks (hours) and fitting in as many as you can, you're trying to do too much. I agree with Michael about the size of your container and the amount of goods you want to put into it. Time can get tight quickly especially if you've made all your lodging reservations ahead of time. You will be pressed for time on such a trip and will end up overstressed or regretful that you had to skip something you were planning on.

I have never had any issue with any car I have rented from any company. I have found that you can save significant amounts of money by renting from an off-airport location. Often such sites are less than a mile from the airport, have free shuttle service, and allow you to return the car to the airport.