Finally, I'm back to getting a little bit done on this project. After getting everything set up again, my first bit of progress is actually figuring out what went wrong with the graphics library and how to fix it. It seems the combination of the adafruit gfx / sharp memory display libraries and the sparkfun artemis arduino core end up doing hw SPI transfers most significant bit first, while the display expects least significant bit first. Not 100% sure where the issue lies, probably in the arduino core, but I was able to hack around it by reversing the bits in each byte before transmitting. Anyway, with that working there's a very nice boost to the screen refresh rate! It was quite distractingly slow.

Got a good tip on how to reduce power usage too, so looking forward to testing that out next!