Olddude: Think you'd enjoy- if you haven't already read them, Annette Gordon Reed's

1. Thomas Jefferson and Sally Hemings; An American Controversy (Univ. Virginis Press 1998)and

2. The Hemingses of Monticello (Norton, 2008)

( Helps to read them in order of publication- I did it backwards )

They deal with quite a few of the issues you've raise.