If they join my Alexanders at all, it's before both groups settled on the NC-SC borderland; however, I am attempting to put together as much as I can on the early Henry County Alexanders. I can't really help, but I've read all of your postings. Here's all I have.
I believe that you are probably on the right track with Simpson or a brother of Simpson. What I have on Simpson and his family is mostly pieced together and unverified. One of Simpson Sr's daughters, Sarah, married Lewis Lafon from the Cottage Grove community, and one of his grandsons by Ivan L. Alexander Sr was named Lewis C. I don't have anything on Smith Washington.