I notice that you are using a different cable for testing on the intercom (3.5mm to 3.5mm). Have you confirmed that you are getting audio at the end of the TRRS cable? I would check that first by tapping the wires onto a pair of earphones.
Have you set the Aux input volume in the 2nd level of the Trig menu? Section 6.2.6 of the manual. Even with the PAW at 10, I suspect you will have to crank it up a bit. If that fails try using the music input on pin 15, for which you will also need to adjust the volume.
Note: I Have made the assumption that you can hear other stuff on the headset jacks?