I was fairly close to getting everything running, and as I mentioned, this last stage is painful in that things *almost* work. I discovered a few new problems:
1. There's a random SDIO error that causes printing to error out. I hooked up Octoprint and proceeded anyway.
2. My travel settings are way, way too agressive for the little MPSM I wired this into. The printer doesn't move fast normally, and you can see it shakes and rattles quite badly during the video.
3. Steppers STILL aren't adjusted right. X skipped a step at the bottom, causing a shift (and at the top, the person operating the printer failed to get their hand out of the way of the print head, causing another).
4. A partial clog midway through the print caused that ugly layer in the middle, a minor shift caused the bulge below it.
Despite all these problems, the printer works. The pins are correct, almost everything works except one of the LCD buttons, which isn't defined right for some reason. I'll begin a PR to get the pins added to Marlin once I have that fixed.