Here are some recommendations and questions:
6. For Arabia, in theory, you could park a Galley outside of Mekka, then kill them when they move all of their units out.
Another method: Found Mekka before they spawn (better on incense, you get commerce for a few turns), refuse flip, their army will slowly approach Baghdad, and their sole settler will stay around Mekka, capture them, destroy a stack of theirs, make peace, and they will never be able to get a city. I think AI doesn't know how to do with this situation, so they'll just idle.