Thanks once again for all the input! (And for the voice compliments!)
I figured out my RMS Normalize installation issue — I somehow had two copies of Audacity installed.
I’ve also used the microphone-on-books trick you recommended, but accidentally, as I don’t have anything else available to use to raise my mic height! I don’t think I’ll be able to find enough friends willing to line the walls though…
I’ve adjusted my mic recording volume so that my peaks are around -6db, and that makes my recording pass the noise floor limit now without any editing. I recorded a new clip and put it through all of the mastering steps recommended in this post: https://forum.audacityteam.org/t/audiobook-mastering-version-4/45908/1 (Equalization, RMS Normalize and Limiter).
However, I’m still not passing the RMS levels. It looks pretty close, though:
What do you think?