There is a wealth of information on Bachman in The Letters of General James Conner (can't recall the author), published ca 1951. Most larger S.C. libraries haave it. Also is mentioned often in Wanener's manuscript diary in the S.C. Historical Society, Charleston. Wagener was a juniro officer in the German Artillery. The Historcial Society may also have a photograph.
The correct spellign of he Birdge is "Braxton's; it wwas located at the crossing of the Salkehatchie River, between what is now Bambery and Allendale Counties.
Can't help on Richard Johnson.