I didn't see much of the practical in this discussion, so here are my thoughts and experience.
There are a number of approaches to mixing. Some favor low volume mixing and there are hip hop and rock producers that mix with very loud monitors (many claiming they need to feel the music). There was a quote I read (wish I could remember the engineer) that said, "the soul of music is in the mid-range". The example he gave was you could be in a grocery store listening to a very frequency limited sound system and a good song come on, you are still going to groove to it. Given the way most people listen to music these days, the approach to focusing on the range between 400 to 8khz makes a great deal of sense.
I only know of a couple of 70+ year olds with what I'd consider great hearing. Since this seems to be the old timers thread, how many here are delivering industry standard mixes and masters? I stopped around my 50's when I shut down my live sound and recording company and left my job at a commercial studio. I've since worked on a few vanity projects with a good friend that I am certain got listened to by at least a dozen or so people. So, first piece of advice, be realistic about what you are doing and why.
I'm not aware of any tools that will allow you to compensate for your hearing but there are a few that will let you visualize sound. I like Izotope Insight for its spectral view so I can at least see how much energy there is outside my range of hearing. I tend to work first on getting a mix to translate well on limited band monitors or my phone first. Then I borrow a younger set of ears at final to make sure there is nothing offensive in that upper register.