Pianist:
I'm over twice your age, but your current hearing condition seems to parallel mine pretty closely. I think in normal range my ears are 'musical' like yours, and I can hear up to 16Khz. Above that it seems to turn to pain rather than hearing. If I turn up the volume on an 18Khz signal and listen for more than a second or two I get a headache that can last for a minute or more.
I also notice an imbalance between my ears' listening ability.
With headphones in particular it feels as though the music is centered a half-inch or so to the right of the center of my head. For that reason, I prefer to use my HD650s at work instead of my IEMs; I can turn the headphone around backwards and ascertain whether or not the music (or music player) has an imbalance or whether or not it's my ears.
Adjusting the L-R volume balance doesn't generally tend to solve the problem. I think that's because the imbalance is not the same at all frequencies. If I'm able to determine a volume imbalance scale, it would be interesting to apply an equalizer to just the left channel and see what happens. I'll have to check out that hearing test website mentioned above.
The imbalance makes it more challenging to dial in my equipment at home for sure. I've got tubes in my phono preamp, my preamp, and my headphone amp. All the tubes are contenders for noise/volume issues, and if I have a hard time trusting my ears then it makes it that much harder to know if the equipment has a problem or if it's just me.
I do have some tinnitus, and the noise is slightly louder in my left ear than my right, by the way. The perception of tinnitus varies from day to day. It clearly gets louder when my blood pressure is higher... it's yet another good reason to stay in shape.
One final thought -- and this is for me as much as for you -- let it go. Accept your hearing limitations, and go enjoy the music anyways. It's fine and commendable to understand your limits, but consider yourself lucky to have musical ears and a mind that's interested in music.
