How to find collector resistor value in bjt differential amplifier
R6/(R4+R6) set a trip point about 4volts. Thus 3.5ma through R1 of 1Kohm.
You can keep R2 at 1Kohm.

Problem is base of Q2: always up near +9v. So Q2 is always off, unless C8 brings in a Large voltage swing.

Does this circuit work? 

Can the 9volt battery even provide enough current thru R8(100 ohm) to swing rail-rail?
Consider making R8 also be 1Kohm.

What is purpose of circuit?