I'm very excited to hear from you. I knew the Hortons were related to the Telfairs, but did not have anymore information than that.
Gertrude Small was my grandmother. I'm not sure how the Johnston name came about; I always thought Julia Boone Telfair was my great-grandmother, but you are probably right. Telfair had children, as did Robert; the other three children had no descendants. Robert had a daughter, Shirley, and she had one son (named Charles, I think). You are right about the name, Julia; my niece is also a Julia! My mother was Barbara Rebecca, Rebecca also being a family name (for Rebecca Southall). My mother was one of four grandchildren of Julia and Edward F. Small, who all had children, and we are pretty well spread over the United States, myself being in Florida.
I would be delighted to hear from you again. You can e-mail me at firstname.lastname@example.org any time.