Diane, I'm not able to find reference to a "Blackwell" SC, so I'm guessing the town name is actually "Blackville." My great-grandmother Bertha Templeton was born in Blackville, SC, which is in Barnwell County.
If you are able to provide the full name of the Templeton half-brother to your relative John Sims Scaffe, I may be able to make further connections.
With kind regards,
Sarah Spencer