If the rental location is convenient, I would go with the rental. Your calculations are largely nickel & dime and based on broad-based national data. Fine if you are looking at fleet economics for a large company, useless for a one-off.

Reason for the rental is that if something happens, you call up, it gets towed and you get a new car. If that happens with your POV, you have it towed somewhere and either wait while it is repaired or you find another rental or take a bus. That is expensive, time-consuming, and presumably the last thing you need on a day with 700 miles of driving.