There are two possibilities that would suit your purposes for your return drive to Louisville. One more on the historic side, and the other more on the scenic side. The first is the old National Road. Today this is US-40 and has the advantage that it's relatively straight and runs parallel to I-70 so if you find that you're running out of time, you can just hop n the Interstate and head home.
The other are the roads that follow the Ohio River. I've driven most of that route and it was amazing to me how undeveloped those roads were considering they ran along a major river.
The choice is yours, but those are the two options that I think warrant further investigation on your part.
AZBuck