I noticed your post was from 2010 but I thought I would still give it a shot.
You mentioned Mosby and other families in the information you have.Could you check if there is a mention of an Edmonds.
I am looking for an African American by the name of Elisha Edmonds, DOB 1816, Virginia possible Powhatan County. Elisha married a Cora Ann ? and then moved to Canada around the 1840's. Cora Ann was from Geneva, New York United States also an African American.I assume Elisha met and married her in New York because of an announcement in a Buffalo news paper.
There may be a connection to the Mosby name and/or a Willam Hickman and Williams half brother Thomas Edmonds.
The Edmonds name has shown up with the spellings Edmunds/Edmons/Edumunds and I am sure there are more variations.