This is really well done. You made a clear effort to incorporate the challenge, and executed it really nicely as well!
Personally I didn't feel that I had returned to the cave (or at least, that it had changed significantly/cleared-out). While the melody was less dissonant and had changed sound, I don't think that was an obvious enough change, it just felt like a B section to the same song. A shift in the main pad/keys sound (brighten it up with an EQ/filter sweep perhaps) might have transported the listener into a more dramatically different space.