Makes sense to me. Your coupling cap for the audio probe doesn't need to be that big (1uf OR 630V). For guitar, a "standard" 100nf box cap will work just fine. If you've got the space you can use a 1uf box cap.
There's probably a solder bridge somewhere. Can we see the back of the vero? It would be a good idea to run your iron down the tracks to clean them up.
They're not all zingers. There are too many circuits out there that simply underwhelmed me. Your building skills are still top notch, though. Nice and clean!
That board appears to not really have a breakout section other than IN and OUT. You’ll have to get a little creative to add a PPCB breakout board, meaning you’ll have to jumper a 9V and GND connection somewhere to it. Also you’ll need to add a LED and CLR