There really isn't a lot to see between Nashville and St Louis. Clarksville has plenty of places to eat but I would check out Ms. Patti's 1880's Settlement near Eddyville Ky to eat. Paducah has plenty of places to eat as well and you can take a detour to Metropolis if you like casinos. Of course Nashville is loaded with wonderful places to eat and things to see.
Between St. Louis and Nashville isn't a long trip - it can be driven in about 4 hours, so you probably don't need a place to stay. You could stop at Burton's Cafe and have some of their famous White Pie (which is a regular pie and not a pizza). And Paducah also seems interesting - they have a quilt musuem, a winery, and Fort Massac State Park
Sierra Yea that route doesn’t have a ton of stuff to do but if you are taking that way I would suggest Paducah as a stoping point to walk around downtown. There are some good places to eat there but nothing spectacular. Land between then lakes state park is a nice area to stretch your legs.