We made a similar trip two years ago - about 1 and 15 min so of you in Dade City. Outbound the first night we stayed Adairsville GA at Harvest Moon RV Park which was about 6 1/2 hrs for us. We left early that morning as we wanted to be north of Atlanta for the first night. From there to Nashville it is about 3 hours or so. We left later in the morning to allow the fog to clear in the mountains as we did not want fog when we went up Monteagle, but we wanted to do the climb in the earlier hours before it got hot out.
In Nashville, if you like more natural campsite I recommend Seven Points COE, but if you want to be close to everything and more centralized, I recommend Two Rivers. We did not find a lot of good choices around St. Louis. We ended staying at Casino Queen RV Park. It was near the Arch, but was secure and safe. Nice level sites with a great night view of the Arch. Decent buffet at the Casino.
Stopped at Morgan Creek State park in Palo, IA. There is a good KOA in Sioux Falls. Check out the Corn Palace in Mitchell SD. There is some RV parking around the block from it. It is about an hour to two hr stop. There is also a nice KOA in Mitchell. After that we stayed at Badlands KOA to sightsee the Badlands and went to Wall Drug. Then stayed a week at Rafter J in Rapid CIty. Loved Rafter J. Spent some time at Fishing Bridge Campground in Yellowstone and Grizzly RV Park in W. Yellowstone. We could not get into Madison. Recommend Grizzly RV park. Fishing Bridge is about location - location.
Cannot help you on the way home as we came back on Hwy 80.
2015 RAM 3500 dually Deep Cherry Red Crystal 6.7 Cummins Aisin 6-Speed
2008 Carriage Cameo F35SB
Jeff "Loving DH"
Smokey & Purrshing, Our Ragdolls
Gordie, Springer Spaniel
True Blue, Aussie