I will definitely read through that prior to refactoring this project into a more normal format. Thanks!
^^^ EDIT: Good grief, this is fantastically simple. Amazing.
Follow-up on SRAM usage: according to Adafruit's quick RAM check function, I still have over 6kB of ram free out of the 8kB on the chip immediately prior to the offending lines of code, so it doesn't look like I'm running out of memory. That's what I thought, but all the same...good.