I am getting to the conclusion that I may have a spinal injury.
Nothing about all this random numbness makes sense of it all suddenly happening in the span of a few days... and specifically, immediately after lifting and manipulating that heavy load at work. My back is still sore, and what I originally assumed was muscle strain may, in fact, be a compressed disc.
That would, at least, make sense with all the numbness.
@JulieSqveakaroo internet medical advice seems to always go to the worst possible possibility, even if it's way more likely it's something simple
-F