So, after another month of maintenance and observations, here are my conclusions. This applies only to my system - I'm not saying any of this is relevant to other hot tubs, as so many people appear to get completely different results than I have with various water chemistry/sanitizing techniques.
1) In an attempt to "avoid chemicals" (especially chlorine), all I did was make my water maintenance far more complicated and expensive. The ozonator, metal ion, MPS, enzyme route was a complete waste of time and money. I now add 2 oz of bleach every 2 days and the water remains absolutely crystal clear for a small fraction of the cost of all the other stuff.
2) The metal ion system does absolutely nothing, as far as I can tell.
3) The ozonator does absolutely nothing, except get rid of the chlorine very quickly.
4) Despite the high CYA, 2 oz of bleach keep the water perfectly clear. As I have no way to test for bacteria in the water, all I have to go on is the level of clarity (and bather health). Using 2 oz of bleach every 2 days is enough to keep the water as crystal clear as it has ever been, even with CYA over 100.
5) Bleach is super cheap and we never, ever notice the chlorine level in the spa. I usually add the 2oz of bleach after we soak, but even if I dose it in the morning, by the time we use the tub in the evening, the FC level has fallen to zero again, thanks to the ozonator. So we seem to be getting all the sanitizer/oxidizer benefits of the chlorine without any real exposure to it when soaking.
By now, the water is four months old and ready to be dumped. I'll probably use the Ahh-Some product during the changeover, though frankly, as long as the water continues to be this clear, I have no issues. All other parameters are stable, so hopefully my next batch of water will also be well behaved regarding pH, hardness, etc. I won't be replacing the Nature 2 metal ion system - maybe the one I bought on Amazon is counterfeit, but whatever, it adds nothing but cost, as far as I can tell. I'll leave the ozonator in, but I have no confidence in its ability to keep the water clean. I actually like the way it gets the chlorine level down quickly, and as long as the bleach does the job, I'm happy. I have plenty of left-over dichlor to establish a reasonable CYA level with the new water before switching to bleach.
My only complication now is if I am away from the house for a few days, as my current system requires bleach every 2 days, but I imagine I can find an alternative for those occasions.