Help check amplifier stability
Stability depends on the gain and phase of the loop gain. That is the complete loop comparing one side of the break with the other. You should be comparing the gain and phase of the signals either side of the inductor. That is to say comparing Vout to the injected signal. 

The complete loop phase must be substantially less than 360 degrees when the loop gain is 1 (unity). Notice that you have 180 degrees lag already at low frequency due to the inverting nature of the combined input stages. So theoretically you're allowed another 180 degrees lag around the rest of the loop at unity gain. In practice a safety margin is included (phase margin of say 45 degrees). So in practice the phase lag around the complete loop should be no more than 315 degrees at unity loop gain.

Also watch out for the phase scale. Where it starts at 180, that would have been clearer if it had been labeled -180 and then increase negatively to -360 where it is marked as 0.

If you find that the loop phase is greater than 315 degrees at unity loop gain then increase the size of C4, the compensation capacitor.