Making some progress in fixing it. Replaced the left rear wheel speed sensor, everything was still borked. Found a broken wire, fixed that, now even more lights are on... Turns out the aftermarket sensor I did the original replacement with (was cheaper and way quicker to get) is garbage and gives random readings, which makes the vehicle freak out even more. So now we wait for an OEM sensor to come in, and the ABS system should hopefully be working again at that time.
On a semi-related note, anyone wanna buy an X? This one is getting old enough and I don't have the time to keep fixing it anymore, so I plan on flipping it for a 2015. If I can find someone quick enough that doesn't have an issue with a vehicle that needs maintenance, I'm happy to get it to a new home. Otherwise, I'm probably just going to trade it in, I don't have the time or patience right now to deal with classifieds and all the morons those seem to attract.