Hi PB! I confirm that the balance pot works, and my Crack amp is up and running just fine. I've been listening for about 30 minutes with no issues.
The balance pot clearly changes the prominence between the left and right channels. For instance, when I crank the balance pot all the way to the right, the right channel becomes more prominent with sound still coming from the left channel. My volume pot is working just fine too.
I threw on some mono tracks to test everything out.
If any issues arise, I will post them here. I really appreciate all of your help! This is a very cool mod.