The voltages on the 12AD7 are within 20% of the schematic, barely, and I would not suspect them to be the cause of the distortion. Especially since the cathode voltages are good. Your heater voltage is a little high, indicating the wall voltage is probably more that 117vac. Again, not a problem but if you can use a variac so that the heaters read 6.3, then check the preamp voltages, you should see that they are even closer to spec.
You said in the previous post that the preamp is clean when you jump it to the other channel, do this should confirm that all is fine with the 12AD7. It sounds like your problem occurs after that. I think you should continue to use the good channel to your advantage to try to identify where things are going bad. Have you swapped power tubes to see if the distortion follows the tube? Are the plate, screen and cathode voltages the same from one power tube to the other? What happens when you swap the plate wires (effectively swapping output transformers? Are your VU meters connected? You can disconnect them for testing purposes. Do both OT secondaries have the 8 ohm resistor in-circuit?
You see where I am going....keep on investigating, focusing on the power amps and the differences from one side to the other.