I'll start off with some context. I'm attempting to set up a dual-boot environment on my Macbook Pro (model 9,1), which is currently running Mac OS 10.8.5.
I've successfully installed Jessie 8.7.1 using the Debian Wiki's guide with 8GB of swap (https://wiki.debian.org/MacBook). The install was a regular web install from USB, with GRUB being placed on the the master boot record of the hard drive. To boot into Debian, I've also installed the latest version of rEFInd onto the Macbook. The Debian partition was formatted to ex3. Both operating systems are sitting on the same hard drive.
I'm not sure if this is useful information, but I have 16gb of aftermarket RAM installed on my Macbook, as well as a second hard drive that I installed by removing the disk drive, which I bootcamped Windows 7 onto. Windows 7 wouldn't boot if it wasn't located on the primary drive, so I had to swap the drive containing Mac OS with the second drive.
Onto the problem. When booting Debian from the rEFInd boot menu, the computer goes through the normal process of loading the operating system, with console output giving me OK messages. Then, the screen flashes white once (I assume that's something to do with graphics driver swapping?), and the system continues to load. Then I hit the Debian teletypewriter screen (Debian GNU/LInux 0 debian ttyl \ debian login: _ ) and then the screen goes black with a single, non-blinking underscore sitting in the top left screen. No keyboard input is taken, and I've tried to load up a TTYL screen using Ctl+Alt+F1 (or in the Macbook's case, Fn+Ctl+Alt+F1). I've tried leaving the computer there for an hour just in case it was just executing something extremely slowly, with no luck.
I've uploaded a video showcasing this process: https://streamable.com/wl35p
Any help would be appreciated here, I'm pulling my hair over something that (should?) be simple. Thanks.