So.... Good news is that PRS+ worked! YAY! So I can now load any font I want to my device. Yay! *happy dance*
Bad news is... they look different on my reader than they do on the computer screen. Whoever called that wrinkle was definitely right -- this is a trial and error thing.
EDIT: I'm also not sure how to tell if a book is over-riding my fonts or not. Where/How does one look in the epub file for font overrides? Thanks.