UPDATE!
I downloaded some testing software, and it turns out that the CTRL keys actually do work! (And all key combinations, as would be expected.) But... the left CTRL (which I default to) is pretty faulty. I have to hit it from the far left of the key in order for the switch to actuate.
Is it easy to repair an ALPS switch? Or will I need to completely replace it? Anyone have any advice on how to proceed? I've done very little soldering in the past, though I do have a soldering iron and some solder lying around somewhere...
Regardless, I am relieved that the keyboard is almost fully functioning. Typing is a blast on this board!
Thanks in advance for any advice!