Alright so the old STEAM drive is totally toast. Hooking it up to my old Win 7 PC in the basement showed the same results as my new Win 10 rig. PC will take quite LITTERALLY forever to boot with the corrupted drive, and once Windows finally boots the only option I'm presented with is to reformat the drive.
However it seems I was working off of the secondary drive on my PC, so the only thing I lost was the "custom" GUI for the mod. I can recreate it, it's just a pain. I won't know the full extent of the damage until I rebuild the STEAM directory. Have to pull up the blank template and start pulling everything back in.
Good thing you didn't lose the whole mod! Although it still sounds like a total pain the *** D: