Ben I wouldn’t give up just yet
I’d use this to learn how to use an audio probe
They’re cheap to make and easy to use and probably one of the best debugging tools
This circuit’s fairly simple so it shouldn’t take long to find where you loose audio
Read the audio probe explained PDF in the guides page
If it was working initially apart from the buzz then as you said it’s more than likely a ground issue if you are using the 3PDT board that would also need to be grounded you can run a wire from the one knob fuzz pad marked S5 to any ground pad on the 3PDT board
Post a nice clear picture of how it is now so we can have a last look it is definitely savable so as I say although it’s frustrating it’s well worth continuing to debug you’ll learn a lot which will stand you in good stead for future builds
I’ve built hundreds of pedals complicated and simple and they don’t always fire up first time I’m currently having problems getting a super simple fuzz face to sound right