OK, I'll just wipe it off and try again, went into TWRP "Wipe", and did all of the wipes. Which is where I went wrong. I did ALL of the wipes. So now the only thing still on the tablet is TWRP. Luckily I can still boot into that, but that's it.
So, this is where the real problem comes in. I need to be able to load the ZIP onto the device root so I can use TWRP to install it, but for the life of me I cannot get my Windows 7 Laptop to recognize the device. I have installed, uninstalled, and reinstalled the Samsung drivers at least 4 times, being extra patient to reset both the computer and tablet after each attempt, i've tried turning the computer on with it already plugged in, i've tried waiting to plug it in until after the computer is fully booted, everything.
The USB port on the computer recognizes other USB flash drives just fine, i'm using the OEM cable, and everything worked fine to connect the tablet with Odin before I did that wipe, so we can rule out the cable being bad.
I've been reading a lot of forum posts both on XDA and elsewhere and I've seen people talking about needing to uncheck the USB debugging in Settings, but obviously I can't get there, because there's no OS. This must have been unchecked before the wipe though, because it connected fine then.