Device to loopback mic to headphones
The headset speaker impedance is 32ohms each and the microphone impedance is 2200 ohms. 


Most of your answer is in that statement. The mic and speakers will act as a potential divider of \$ \frac {32}{2200+32} \$ giving about 1.5% of the mic output (which was already a small signal) to the 32 &Omega; speakers. It won't work.

What you are seaking is called "sidetone" and was used in ordinary old-fashioned telephones so you might gain some insight by searching for telephone sidetone.