heya, here are the AC sweeps for different settings of the potentiometers; using your tracing up here,
AC sweeps, V, I and waveforms are the same when C10, C11, R8 and C15 are jumped.
same for when C12, R10, D2, D3 and D5 are omitted.
Very slight difference in the high end when C8 is jumped (C12...