Well, I am absolutely sure that I downloaded the correct font, the very one that is linked from the Escape Pod AA description (the Font Pack). I installed only this theme and the font pack on top of a fresh build of Rockbox, so it wasn't accidentally getting the wrong version of the same font from a different theme or anything.
HOWEVER - the issue is with the font after all. I experimented with different fonts, and any that have "14" in the name seem to be the right size for this theme.
So, I'm guessing the "wrong" version of the helvR12 font ended up in the font pack or something.
I will try the test you indicate, but since it now works if I just use a different font than the one the theme tries to use by default, it's perhaps less important.
Thanks for the reply. I'll let you know if I discover more.