gonzo

The caps would need to be in parallel not in series. You could get a double throw switch and just have two wires run to the board cap...

Could be both. I would check the wires going to the board to the switch first before pulling anything. Bypass the switch with...

Not the original switch in there. That would be my first guess.

I just draw the schematic and any notes on the inside lid of everything I build. Mainly in case something eventually goes wrong.

You could try a 1M resistor to ground at the input and output. Alligator clip them in and test it.

Finished this up this week. This is my slightly tweaked version of an emulation or recreation of the drive gain circuit of a Silvertone...

Are you trying to change the output impedance to work with the fuzz? True bypassing that pedal will not be easy, if not impossible.