Fascinating read, and excellent research.

I assume you're familiar with the John Henry related ballad, This Ol' Hammer/Spike Drivers' Moan? https://www.balladofamerica.org/this-old-hammer/

It's a bit more defeatist that the regular John Henry songs, a sort of post-partem reflection on his life and death, but if you haven't it could certainly supplement your research well.

You can see some previous discussion of the song here as well as numerous other threads on Mudcat