Ambroxol is not much of an "anti inflammatory". You probably are feeling the effects on your ET resulting in less pressure build up if you feel those effects. The humidity from a warm shower may be helping open up your ETs as well. It is good for facial pain as well through sodium/calcium channel blocking effects.
The "feeling your ears vibrate" is a typical symptom of TTTS and it sounds like you may have that. The Wim Hof breathing may have somehow caused an inflammatory or hypoxic condition in your middle ear that triggered that.
This goes into detail about what can happen after an acoustic shock:
An Integrative Model Accounting for the Symptom Cluster Triggered After an Acoustic Shock
But I think you may have aspects of it despite no noise trauma.
"Irritating" noise seems to trigger the acoustic reflex more because there is a mental component to that symptom (stress or even just thinking of a loud noise can cause a spasm because it's normally a protective reflex which in this case is dysregulated) which would explain why some noise triggers spasms more.
You seem to be looking at treating this like a strictly inflammatory disease and I think you are oversimplifying it.
Hyperacusis takes months to sometimes years to improve but the most important thing is protecting your ears from noise. If you are regularly exposed to 90 dB factory sounds it means your hyperacusis is not that bad and that's a better prognostic factor for faster healing but wear good ear protection around those sounds whether they cause a flutter or not.
As an aside, the ear drum vibrates in a more discordant way for higher frequency sounds.
In any case, I think LDN is barking up the wrong tree personally. LDN is useful for things like auto immunity but the problem with the inner ear is that the opioid receptors actually contribute to NMDA hyperexcitability through an endogenous opioid peptide released during stress called "dynorphins". It's possible for LDN to make you worse and in fact some people do get worse tinnitus on it.
Personally, I think you should 1) protect your ears, 2) use Ambroxol to keep your ETs clear if needed (even just once a day at night), 3) manage stress as well as possible, 4) be aware if you are clinching your jaw or grinding, 5) don't do things to irritate your ET like Otovent or Valsalva since it seems like it's already irritated, 6) don't increase your intracranial pressure with things like the inversion table you were looking at, 7) try as much as possible to relax and not hop from treatment to treatment or expect immediate results. It takes months to see effects.
@Aaron91 has been talking about Stamet's stack. It may help with stress especially (which is a co factor in this) but I haven't tried this yet.
My plan for middle ear healing is noise protection, Ambroxol nightly, walking at night in the quiet to increase middle ear blood flow. I tried Lion's Mane but it seemed to spike my tinnitus (but settled thankfully) which shows you how individual this all is. After 3 months, I'm about 10-15% better and that's actually really good progress for this to show you how slow it tends to be.