hi,
I just came across this thread. you've done a great job explaining transistor bias using the fuzz face circuit.
one thing I should mention. you say:
"Q2's collector current flows from the 9V battery thru R3 & R4. Q2's collector voltage is Vcc - (R3 + R4) * Ic = 9V - (5170Ω * 650μA) = 3.36V...