The cavity pole was measured again. This might be the best measurement of the IMC cavity pole.
The attached plot is the TF from SLOW_OUT to IN1 of the IMC servo. The IMC was locked only with the PZT at this measurement. The results are as follows:

Cavity pole: 6.86(2) kHz 
DC gain: 2.692(3)

From these numbers and the PZT actuator efficiency 3.0 MHz (13012) and FSR 5.62 MHz, we can derive the following parameters

Optical gain: 0.897 V/MHz
Finesse: 409