The $.54/mi is for tax purposes. It has ZERO to do with vehicle maintenance. Tires, brakes, and oil will amount to ~1800 PER YEAR. The 100k miles per year put on the car is going to mean you need a new car in a few years. (I've seen what a Prius security guard car looked like after 360k miles.)
Also, where the hell do you live that you'll use $70 worth a gas in a 300mi day? At current prices, that's 3 full tanks for me -- @550-600mi per tank.