David Knight b. 6 May 1726 St. George's Parish, Baltimore, MD d. aft 1776 s/o Thomas Knight, schoolmaster, ( 1692- 1760) and Susanna Simpson (1692-1798) both of St. George's Parish, Baltimore Co., MD. This info is in church records and in a book called Baltimore County Families 1659-1759 p. 388. All 3 of these people are supposed to have died in St. George's Parish, but I have no sources for that. David Knight appears on the Harford, MD census in 1776. Church records in MD show marriages for all of Thomas Knight's children except the youngest, David Knight. That's all I know with any confidence.
In the realm of conjecture...there is a David Knight that shows up on the 1755 census in NC. I also found this reference:" "The Knight Family" 1975 by: The American Genealogical Institute- on page 48 under NORTH CAROLINA: both David and Thomas Knight are listed as family heads in Salisbury District, Guilford County. This is for the first Census (1790) of family heads for the original 13 States." Could this be David's sons, David, II and Thomas? Afterall, all of David Knight,II's children were born in SC. Or could it be David Knight himself? Could your 1800 census data be for David Knight, II?
Also, do you have dates for Hannah Shockley? I have 1776-1870 (no sources). She and David Knight,II had a son Salathiel b. 1803. But if her father then is Salathiel b. 1760(no sources), then she's born 15 years before any of her siblings.