Bob,
I suspect you are being sarcastic. The Makran caost is close to the Gulf, so it was pure geography. Secondly, both Oman and the Qwasim state (modern UAE) controlled ports in Makran, infact Gwader was Omani till 1958. So easy keep slaves there, before selling to the others.
But let make it clear, not all Makranis are black, infact the majority are Baluch tribesmen.
On your first point, perhaps its worth opening a thread. For the record, I am not a Pathan.