1. It's in the room with the VCR player, the corridor that loops around.
2. Black key is in a locker in the room you get the first hand. It's the 'keep locked' door next the barricade. If you're getting the black key for the first time you need Cleany to open it with trash. Once you get black key though you can open this door and the door to RUST without any need for trash.
3. Rusty knife is in a locker after you get cleany to open the RUST door, just go through the door on the left and it's an open grass area with 2 lockers. Knife is in the left one.