Well. I'm stupid. I thought when I deleted it a year or so it deleted the mod too, and assumed Verifying the game cache would have taken care of that if it was the issue. It was an old mod. Thank you. A moderator can lock or delete (I would, but I don't see how to delete thread in edit options). Sorry.
I fear that this is something really simple and I'm just being dumb, but a quick google search game me no answers, neither did restarting the game, verifying game cache, and making a new world. Inventory is surrounded by a green box; and while I can trash everything, craft things, and grab things; I cannot move things around in inventory, put them on the quick use slots, or place things into the inventory. The green box is pretty much dead and can't be interacted with.