Re: Where did the Black Stone held in Ka'bah come from?
This is all conjecture and speculation. Nothing more.
And since you are keen on linking paegan practices/shirk on Judiasm/Christianity, I'm sure you aren't surprised to learn that many believe Islam follows some paegan practices, Arabic cultural practies and a form of worship toward Muhammed. You also won't be surprised that non-Muslims equally do not believe in the infallibity of Islamic scripture or as an accurate historical source.
So it s all boils down to perspective, biases, faith and beliefs. No one can call the other wrong, but I fail to see any proof here that the ritual of the kaaba was in any way part of early Abrahamic beliefs.