all right, here are a few points from both topics, but I have a hard time getting if you're tackling a complex matter with basic approach because you have most of it figured out, or if it's because you're more lost than you think ^_^. so don't mind if I'm being captain obvious from time to time.
1/ are you clear about the EQ you should apply and what you're trying to do in general? the graph given by an audiologist is usually showing a result compensated for equal loudness. meaning that if you have about average hearing, then the graph will end up close to flat.
but if you're at home and use test tones to judge by ear if some frequency is getting louder,
you will not get the same graph. I'm not sure if you are already aware of this or not, so just in case:
https://en.wikipedia.org/wiki/Equal-loudness_contour
2/ you have an issue turning a graph into an actual correction EQ. that is very natural. you have at least 2 issues:
2A/ a headphone isn't flat. so what can be fairly simple to do on your speakers, is much more complicated on headphone. you can of course decide to apply the same correction and say "F it! I'm leaving the headphone the way it is". but that could leave some massive variations that may or may not add up to your already massive EQ. so it's not easy to tell you if you'll be satisfied, and it's even less easy to tell you if you might finish ruining some frequencies in your ears with some involuntary extreme boosts.
2B/ if you apply EQ on multiple bands, there is of course the possibility that in some places the curves will interact with each other.
here is a bad example:
the colored areas are individual EQ applied, and the white line is the actual correction I can expect. depending on settings, they can match exactly, or be very different. where I placed my cursor you see in the box the settings I used and I asked for a 4.4dB boost near 2kHz. but the white line is far from it, you can read the actual boost I'll have on the top right, "graph: 0.13dB". that is the result from that boost plus the surrounding EQ settings.
3/ is the matter of having a device and a headphone able to apply a good enough EQ. by good enough I mean with more than kiddo settings so that you can decide how high and how wide some bands should be set. not all EQs will offer something like a 30dB boost(or attenuation). with portable gears you'll often get 6 to 10dB max(10dB feels twice as loud).
then however you plan to set your EQ, let's say you want a boost of 20dB at 5kHz, in the end you'll need to have 5kHz as is, and reduce the rest by 20dB(to avoid clipping the signal). so you'll end up asking your amplifier (or amp section of the portable device) to go in this example, 20dB louder than your usual listening level. it could be a challenge for some sources and some headphones.
that concern was brought up in the other topic. it's a double issue. first you need a headphone that is able to do your preferred loudness plus 20dB or whatever it is that you wished to apply. and next is the amplifier, that needs to be able to give you your normal loudness+the 20dB to compensate the EQ attenuation.
you might not actually need a full 20dB depending on the headphone's signature and part of your EQ, but it's fair to start with that much in your estimate when looking for the right gears.
so you do need a fairly sensitive headphone, one that already has a bright signature would be a good idea. an even better idea would be to see a max SPL value given in the specs(when you'll blow up the headphone of melt the coil). they don't always provide that. I'm guessing if you contact a brand and explain your situation they will give you the number, but you never know.
if you're a quiet listener this might never come to be an issue, but again it's always better to know where we stand.
and of course you need a source that will be able to push your sound at your desired loudness+the value of your max EQ. we can get a fair estimate of that for amplifiers, but it might be less easy for some portable players where specs are often scarce or incomplete enough to be useless.
3/ is it bad for you?
in the end it's obvious that by making the frequencies you can hardly hear way louder to get them fine again, you're also likely to accelerate the speed at which you might completely lose those frequencies. all being a matter of how loud and how much time you spend listening that way each day. but that's the issue with any hearing aid. you decide to get them because the situation without them is too bad anyway. so instead of the idea of ruining your ears, it becomes the possibility to enjoy sounds a little longer thanks to the aids.
doesn't mean you should go crazy, and in general I would still advise to try and get the supervision of some medical professional. but if I was in your situation, I would probably be doing exactly what you're planning to do.
none of the stuff I mentioned are impossible and even really hard to improve or check at a practical level( well, getting the real flat EQ for your ears is something all audiophiles struggle with on headphones). but the sum of them could make for quite the work in research, learning, and testing mostly.
