So, this mac had some graphics card drivers that were potentially corrupt. After moving them out of the drivers folder, I'm able to boot in normally. However recovery boot isn't working, I can't get it to update via the App Store, I can't open Finder, nor can I do a myriad of other things. I need to re-install the OS, but can't seem to find any way of doing it... my only thought is that I could re-install it via single-user mode which is the only thing that seems to be working perfectly fine.
How do I re-install my OS from single-user mode?
EDIT: Well, I found out why it wasn't booting into recovery boot: the graphics card drivers for the main system weren't working - for the same reason the drivers in the recovery partition were not working, both on the computer's harddisk, and on the recovery usb I made. After disabling (moving) the drivers on the usb, it booted to it fine. The issue is the graphics card hardware.
Nonetheless, I'll leave this question here since it's still a great question that deserves a good answer.