That’s a great analysis. And as they say, “Not everything that can be counted counts and not everything that counts can be counted”... and the uncountable here is the human behaviour... there is certainly difference between “what should happen” & “what actually happens”... human emotions & experience does make a difference. I believe the behavioural reaction of rate cut from 6% to 2% is not the same when they are cut to 0%. Latter is bound to invigorate animal spirits & in the end moral hazard. Also Japan 0% may not have impacted it’s P/E but would have certainly impacted the valuations elsewhere with carry trades...
In short, the low rate may not have a linear relationship with stock market PE, however, the second order & third order impact on overall global asset inflation cannot be ruled out in an (hitherto) inter-connected world.

PS: loved your insights & analysis!