You've probably considered this already but are you expanding your search to include neighboring counties in Ga?
Also, since I'm not well versed on the history of Edgefield, I came across information regarding the Hamburg Massacre. Being that this was a black community in Edgefield it may be worth it to research news articles which may reveal information about your ancestors. I'm always fascinated with what others are able to discover about their ancestors. I'll be sure to take a look at your tree.