Before we moved to Virginia and became farmers we lived in Florida and traveled every year for 3 weeks, driving all over the US. So anything you want to know , you can probably ask me, don't think all that much has changed in the last 6 years ( last big trip we did was 6 years ago, drove from Florida to Washington State , and various other places , put 11000 miles on my truck in 3 weeks....).
Your trip is not bad, you are not driving through any terrible traffic areas ( like Atlanta, or DC, or Houston). Nashville can have a lot of traffic, so plan extra time for that. My advice, check your google map frequently for accidents or other traffic jams , and if there is a big one ahead, get off the interstate and go around it. Nothing worse than being stuck in a interstate traffic jam for hours.
St Luis: been there several times, the Arch is interesting, has a little museum at the bottom. Is it even open or shut because of Covid? If you are allowed to go up to the top, it is very claustrophobic and sort of scary on top and on the way. I was glad when we were back down. I am not afraid of heights but I didn't like this.
We also went to the oldest Lutheran church , and on a boat trip. Again, not sure what is open now. Beware, most of St Luis downtown is scary ghetto, don't get lost, don't get out anywhere except the touristy areas.
Have fun!