This is amazing. I love the setup and the artwork; the cover is especially brilliant. The car is such a great idea, I wish it was more prominent at the end there. If you ever come back to this it could be so cool to have the party vs the Knights of Rulf (or Beleth) in drag race through hell to reach the magic stone.
Genuinely, I had so many ideas reading through your entry, I would definitely run this for my group sometime!