On the braedboard I have a similar schematic, but just a couple of 1N4148 diodes.
I got about the same volume drop with the More pot at low settings. Even less distortion.
I tried another 5k pot, different transistors bought from different shop (2N2222A, 2N3904, 2N5088, 2N5089). None of these give me more volume at min More pot setting, and I don't think I reach the same amount of distortion I can hear in the demo. The ones with higher hfe give me more aggressive tone, but nothing more.
I tried to jumper the 330R, in this way I got more grit sound at high gain setting, but still low volume at min.
I build pedals