Samsung Galaxy S3 — Bricked Galaxy S3...?

Hello,

I've tinkered around with my Galaxy S3 a little too much, and it currently is unusable. I will try to recapitulate every steps I've made until now, so that you get every details you need.

A few months ago, I've decided to root my Samsung Galaxy S3. Model is SGH-T999V which is a version sold by Videotron, a local eastern canadian company. I've rooted using Odin3 and the CF-Root-SGS3-v6.4 file.
The root was successful, however my device began slowing down considerably. I figured the version was very old, and this might have been the cause of it, so yesterday, I deciced to update my software (which was still in 4.0.4 for the initial rooting process).

Being using Triangle Away and SuperSU Pro, I was able reset flash counter, but the device was still considered "Modified". I've watched a few videos, and figured a trick that disabled SuperSU for several minutes after boot to allow for OTA updates, which worked. I let the updates do their things, went to sleep.

This morning, I wake up to a 4.1.2 version of Android. I believe this is not the latest version for my software, so I check again for OTA updates. My device still considered "modified", I try to reset flash counter by using Triangle Away. Here's where the ** hit the fan...

For some reason unknown to me, it seems the OTA update unrooted my device, because I cannot grant Superuser access to Triangle Away, nor can I access SuperSU. I download an app to verify my device is rooted, which tells me that my device is, indeed, unrooted. I then run download mode, which tells me that the flash counter reads 1 and the rest is custom... I read on a another forum that this issue can be resolved by "wiping cache" from recovery mode, but after doing that, my "firmware upgrade ecountered an issue". I believe this might be related to Kies screwing up my drivers or something, not sure. Anyway, the phone asks me to use recovery mode in Kies to fix this... but Kies cannot identify my phone when I plug it in!

I believe reflashing a rom through Odin3 can fix this issue, but for some reason, I get an error code and the installation fails. Here is the code:
Added!!
Odin v.3 engine (ID:4)..
File analysis..
SetupConnection..
Initialzation..
Get PIT for mapping..
Firmware update start..
recovery.img
NAND Write Start!!
cache.img
FAIL!
All threads completed. (succeed 0 / failed 1)

Help me as well as you can. I need my phone BEFORE tommorow ideally, so continuous assistance would be greatly appreciated.

Thanks in advance, and if you require additional information, I will do my best to provide.