"I am very interested in the Davids you all are discussing."
As a descendent of one of them, of course you are!
Samuel & two of his sisters certainly moved on to Mississippi, according to census records, but two of the sons of David & Ruth (Vance) Abernathy who remained in Jefferson County AL have descendants still remaining in the surrounding area today.
Evidence suggests that these Abernathys are closely related to ones that go back into south-eastern Colonial Virginia prior to the Revolutionary War. Alas, we still have not been able to identify the parent of David Wilson Abernathy (cir 1767-cir 1847), so we still don't yet know to which of the many tangled branches he (and you) might belong.
Are you aware of that Abernathy family in 1840 in Tuscaloosa County? We still cannot yet definitively connect them to ones in the Bessemer area of Jefferson County.