This is a complex and thoughtful discussion, and it'll take me more than a couple of reads to respond to appropriately.

But I'll give you one response first since you mention diet: About 3 years ago, I started worrying about memory loss (I'm probably a few years older than you) and did the basic research on nootropic supplements. I was reassured to believe that I could solve my problems with the right batch of pills. There was what I now think to be a placebo effect--then I started changing supplements and timing--no difference. Overall, my memory loss didn't seem to change much (ignorant guess: Bacopa may have made a little difference in terms of concentration but not memory; the others really didn't have any impact that I could pinpoint). Ginko, which you mention, didn't seem to have an effect. Tumeric-ginger and quercitin are certainly immune system builders, and beet root is good for heart / circulation.

With COVID, I starting watching my diet (and doing basic research). After eliminating what are called "ultra-high-processed-foods," I noticed a significant (not placebo, not Hawthorne) improvement in short-term memory, and a decrease in what's called brain fog. If you haven't done so already, you should notice a significant cognitive and immune system benefit from substituting potatoes for potato chips (crisps), apples and oranges for fruit juice, extra virgin olive oil and avocado oil for vegetable / seed oils and fats, etc. The effests of the switch may begin to become evident in than a few weeks.

Best wishes on your continuing journey to health ahd wholeness.