Well this is good - at least you are getting a reading now. Congratulations on that!
This looks like one of those things that will be a long slog to find out what's going on - just a heads up!
Since the voltage is higher than expected, and the touching behavior is unusual, I suspect there is some other noise source louder than the filament hum. So I want to go looking for what it might be.
Before going further, I assume this is an older Paramour, on the 6x10 chassis, with C4S, and using the old plate choke as a power supply choke (the old upgrade). As a caution, make sure the safety ground wire from the power cord is in fact connected to the chassis plate and to the signal ground, and that the power socket has a good safety ground.
Assuming you don't have an oscilloscope, perhaps you can connect a speaker and listen to whatever noise it makes, while touching / not touching the potentiometer shaft. Can you hear a difference? What does the noise sound like? Do you get the same effect touching other parts of the chassis plate? Can you hear a difference as you turn the hum pot? If so, where in the rotation is the quietest? How many degrees either way can you rotate the pot before you hear an increase? Have you done this on both monoblocks?
Obviously what I am asking for is more data - we don't have enough on the forum here to make good guesses, so I won't make any just yet.
By the way, when I make low-voltage measurements, I twist the meter wires together for as much of their length as possible, to preclude measuring the ambient magnetic field instead of the circuit - worth a try.
