Thanks for the reply!
Which part of the rotation is that? Are you comparing your setup with a 100K or a 50K pot? The 47K load (R3 on your sch) has a huge effect on the tone network.
There are as many opinions on how a BMP tone stack should be constructed as there are BMP builders. I'm no exception. I use that style tone stack on many of my designs, and each time it's a little different.
Same goes for the SUSTAIN pot. Some folks like A-taper, some like B-taper. C4, C5, R13 and R19 (on your sch) interact strongly with the SUSTAIN pot near the max end of rotation.
For a simple circuit, there is a lot going on in the BMP.
Those collector voltages are as I expected.