Hi David. Good and important topic, and thanks for branching this to another thread instead of clogging my repertoire.
I would normally not post anything, but I will make an exception in this case for two reasons: first, because this was brought up in my thread prompted by my reference of "piano for mental challenge"; and secondly, because in that thread I outed myself as neuroscientist.
In your 7 points list, there are valid points; anything that decreases your stress levels, improves your mood and is benefitial. Enough benefit to counteract progression of a Neurological Disease? Probably not: current scientific data is not firm on this, but it does not hurt to try. And at the very worst it will do nothing, but will not be detrimental.
Top science-based items in your list: rest (7 hours better than 6), short naps particularly after mental or physical exercise (long naps are linked to decreased motivation), spirituality, stable love life, brain exercise (music, reading, etc). Diet is important, but it varies a lot with genetic background, so it is almost impossible to have conclusive evidence that vegetarian diet is better.
About the supplements: in your list, the only one that is scientifically well established to have a beneficial long-term effect on cognition is the one you ruled out: caffeine. The many vitamins, zinc and quercetin are already covered with a good diet (particularly in a vegetarian diet, and for that reason they are probably not critical), and although good, there is very few (if any) consensual evidence that they are actually beneficial for preventing cognitive decline. And I am sorry to say that, at this moment in time, Lion's Mane is still in the category of "snake's oil". The scientific studies that the Lion Mane sale promoters like to cite, are all sketchy (which is ironic, because those sale promoters do not accept the validity of covid vaccine studies, but are ok with worse performed studies if they help the sales of their products). Does it help in preventing cognitive decline? No strong evidence that it is beneficial, but there is also no strong evidence that it does nothing. So, I sit out on this one, but my bet is that it will eventually pan out as being no better than a good glass of water.