Lucifer Sam
الموت لأمريكا
The origins are older than the Old Testament. I think the first mention of head covering goes back to ancient Assyria in the 13th century BCE.
You are right about Khadija - although much of that was PR to win over her tribe, the Quraysh, which was key to his development as a political leader in the region. Mohammed was a skilled tactician, I will give him that.
As long as we're agreed that Islam does not mandate a husband to limit contact with his wife to sex only. Allah will not suffer misrepresentation.