Ben, I can't answer any of your questions, but, since I have a Blocker ancestor, Sarah "Sallie" Blocker, b.2-22-1797, I want to know who she descends from, also. Some say she was b. in Ireland? I don't know, but she was in St. Barth. Parish, Colleton Dist., SC, by the time she married Abram Ebenezer Beach in Colleton, in 1815.
What I think, is that your George Blocker was married by the same Methodist minister that tied the knot for Sallie. He was Rev. Richard Bryan. Most of his weddings seem to have occurred in upper Colleton Co., the area from Jones Swamp (about 3 miles above Walterboro, SC) to the Barnwell Dist. (modern Bamberg Co.) line.
George Blocker & Mary Gaskin were married by the Rev. Bryan on 5-14-1799. I suspect that he is the guy that got, in 1801, 1000ac on NORTH'S Branch & STEAUBER'S Branch, COLLETON, & in 1803, 534ac on HORSEPEN BAY/BR., BLACK Creek, SALK.R. [this from SC Archives sources, Columbia, SC.] I think he is also the man that you cite in the 1810 Colleton census.