Your findings about Paṇḍu Kambala Rock are very interesting. Thanks!
SuttaCentral
It is great you pointed out this This one time, the Buddha was staying among the gods of the thirty-three at the root of the Shady Orchid Tree on the stone spread with a cream rug.
“Ekamidaṁ, bhikkhu, samayaṁ bhagavā devesu tāvatiṁsesu viharati pāricchattakamūle paṇḍukambalasilāyaṁ.
I recently wrote about the Lomasakaṅgiyabhaddekaratta sutta (MN 134) and its connection to Abhidhamma Lomasakaṅgiyabhaddekaratta sutta (MN 134) and its connection to Abhidhamma
So this long post of yours is very worthy in pointing out these additional connections _ i expect that it will help more people understand that the Abhidhamma was indeed the word of the Buddha.