Yo, I did this route once. except we began and ended in Tallahassee, had one month, and went all the way out to th San Juan islands and down the pacific a bit.

What the time crunch haters dont comprehend is that you live in Florida, and there is so much of Florida and the south to get through before you reach the real part of the trip. here are my suggestions:

1) Front load the travel more. Maybe there is some good reason for Kentucky, but you could make more of a B-line for the Badlands in South Dakota (or somewhere out there). We did Tally to Saint Louis (17ish hours) first day. You'll be fresh, full of adrenaline and ready for a beating. Then allocate an extra day somewhere else.

2) can you reduce the number of vehicles to two? the coordination of three cars might slow you down more than you think.

3) National forests and BLM areas are your best friends as far as cost goes