Ok here you go. (I also noticed the high was set to 170 and low to 150 with a diff of 10 and I'm wondering if that should be 180H and 160L or if it's close enough)
In case anything isn't clear, I jotted down the following notes:
To the L1 screw is the black from the main switch (hot I assume)
To the L2 screw is the white from the main switch
To the B1 push on post is the red from the main switch
There's a yellow wire coming in from the main switch (on the bottom) that is just coiled up and not attached - bad or ok?
The yellow under the H dial goes to YL on the control board - this looks like a permanent connection - not screw or push on
The red under the L dial goes to RD on the control board - also looks like a permanent connection
White from the DIFF dial to WH on the control board - permanent connection
From the push on post top left is a black wire to BK on the board (permanent connection)
From the push on post top right is a blue wire to BL on the board (permanent connection)
Thermostat wires to T and T at top
I'm guessing it's the red under the L dial to RD on the board that needs to get cut (looks like it can't just pull out or unscrew so it's a pretty permanent change) but let me know what you think. I guess it could also be the blue wire (purely based on location related to H and L dials)
Also, if I did want to put said wire to cut on a switch, can I just run wire up out of the box next to the T stat wires and over to a switch somewhere. Not sure where I'd mount that......