No disrespect, but if you operated any instrument at 100dB Leq Av. all the working day you would quickly deafen yourself. No music instrument runs at this level unless it’s a constant drone - peak and average values are hugely different due to the temporal nature of the music. It’s nothing to do with a musician or non-musician it’s the average weighting of the exposure. Even a drum beat at 130 dB doesn’t have a an AVERAGE SPL over 100dB unless you have a really high BPM.
You point about distortion is quite right: I couldn’t understand why the original question assumed that there would be significant input distortion. However at very high input levels, you’re either likely to get peak clipping occurring with the receiver or the aid electronically implementing the MPO, both of which will sound like distortion as they square-off the peak of the sinusoid.