None of your substitutions would keep it from working, if you meant C12 = 15n (C2 should be 1n.)
Your audio probe trace suggests Q1 may not be operating. I'd check voltages and continuity around there, including R2 and R3.
Voltage for Q1 is: C 8.26, B 7.50, E 8.19. Is this normal? they all seem to be in a similar range. Same for the other transistors.
Q2 is: C 8.62, B 8.27, E 8.20
Q3 is: C 8.58, B 8.14, E 8.19
Q4 is: C 8.56, B 7.93, E 8.19
R2 - 8.28
R3 - 8.20
I tried disconnecting the power and measuring the ohms between various points. I hope this is the right thing to do:
Q1 collector and base 255k
Q1 Base and emitter 160k
Q1 collector and Q2 base- you're right, about 1 ohm.
Q 1 emitter and ground 992ohm (as you said, about 1k).
Is any of this useful information?