Unfortunately, I think you now know everything I do about that family. I have not put a lot of effort into them because I decided they were Rigby. I do have some information on Enoch, who is probably an uncle of your William:
There were a couple of black Rigsby families in Dallas/ Monroe/Wilcox after 1870, but they were the only other Rigby or Rigsby in the area.
>Do you know anything about the descendants of this Charles RIGBY/RIGSBY from SC?
Charles was born probably around 1776. He had two sons that I know of, William and Absolem. He lived in Orangeburg Dist SC from 1800 to 1830. After that he and William moved to Colleton Co SC. Now that I look at them, it's not likely your Thomas is from their family.
I had thought Enoch might be related to the William Rigsby of NC who moved to GA: