I am not a doctor, but I do have a little insight into this.
Meniere's was one of the many things that my first ENT didn't quite rule out, but never diagnosed either, when I had hearing loss in my right ear some years back, along with severe tinnitus. Over the years, other ENTs have reached the same absence of a conclusion. Apparently otorhinolaryngology isn't an exact science.
The fact that I didn't have vertigo, which is the hallmark symptom of Meniere's, further complicated the matter. And believe me, ENT docs have tried their best to induce it in me, to no avail. If I had Meniere's, they could have treated it. But without the balance symptoms, they couldn't.
I've also had more CT scans and MRI's than anyone should have to endure. You know what sucks worst about MRI's? The smell. All MRI machines seem to smell like vomit. I don't care if they just came out of the box. They all smell like puke.
Some of the things that were ruled out included syphilis, MS, aneurysms, acoustic neuroma, rabies, lupus, and many other diseases. But nothing was ever definitely diagnosed. The VA thinks it was a result of a live-fire drill in GTMO that caught everyone on deck by surprise, so we didn't have hearing protection on. The last civilian doctor I saw about it said it was "idiopathic," which is doctor talk for "I dunno." He suspected, but didn't actually diagnose, Eustachian tube dysfunction.
In the end, a Chinese pharmacist who had been a doctor in China told me to restrict sodium and prescribed herbs. I've experimented over the years and found that the two that seem to work best are vinpocetine and lemon (not "citrus") bioflavanoids. Others that he prescribed included licorice root and ginger, which I have learned are more for the nausea, which I wasn't experiencing anyway.
What the vinpocetine and and lemon (not "citrus") bioflavanoids did do was restore most of my hearing, and on most days, eliminate the tinnitus. If I eat a salty meal at night, I'll probably wake up with some tinnitus. Other than that, it's a non-issue.
So what can I say? You have symptoms that are notoriously hard to diagnose. It's also possible that you do have Meniere's, in which case an attack at altitude most likely will kill you and your pax. So do everything you can to find the cause and treat it. Consider a doctor who specializes in balance issues. And in the end, if you don't get satisfaction, talk to your doctor about non-traditional treatments.
If nothing else, you may want to talk to your doctor about sodium. I have learned from ENT's and personal experience that sodium aggravates all kinds of inner-ear issues. The most succinct advice about sodium I ever got was to try to avoid it completely because in America, there's no way to do that, anyway; so by trying to avoid it completely, you may just limit it to a healthy level.
As for your medical, all I'll say is that this whole experience was one of the reasons I decided to go SP (and more recently, 103). Apparently the FAA frowns on symptoms without explanations. An AME in Queens told me that until I got a diagnosis from an ENT one way or the other, getting a medical would be a challenge. "Idiopathic unilateral hearing loss" and "possible Eustachian tube dysfunction" are suggestive of too many possible maladies, and ruling them all out would have cost a fortune.
Rich