Finally had a chance to get back to this. I've gone ahead and taken a video.
https://www.youtube.com/watch?v=gLhlQPAO7_4
I tested the AF output again, this time with a direct connection to the same speaker. Still no tone. So I opened it up and ran some continuity and value tests on the AF section. Everything in the AF section (including the wires to the AF out socket) shows continuity and appears to be within tolerance.
I traced the filament pins of the 6C4 tube to where pin3 on the 6C4 connects to pin 4 and 5 on the 12AU7. I discovered that pins 4 and 5 on the 12AU7 appear to be soldered together, which seems odd to me, but it also looks like it works on the schematic.
One question I do have: is Pin 3 of the 6C4 meant to connect there? The schematic I'm looking at is a little blurry, and Pin 3 there leads off to either an M or an N or an X or something. Pin 5 on the 12AU7 has another hard to decipher mark on it. I think those two link up but maybe someone with a better schematic can confirm. If my 6C4 is miswired of dead, that looks like it could kill my AF out.
I also need to check my pot values, but I'm not sure how to test when I have the three pins coming out of it. Any notes on how to best check the resistance reading on one of those?