I can't help with the death date dilemma, but I do have some information about the guardianship.
From Fauquier Co. Virginia Guardian Bonds 1759-1871 abstracted and compiled by John K. Gott, p.12 "Chilton Ransdell, gdn. of Maria and John Ransdell, orphs. of Thomas Ransdell, dec'd.26 Sept. 1796. For: $5000.Sec: Orrick Chilton, William Ball. Wit: O. Gwanthmey."
Please note that this does not indicate that Thomas died on 26 Sept.That was the date of the bond being issued by the court.The original bond is contained in either loose papers or bound Order Books at the Courthouse in Warrenton, VA.According to the author, the original bond should indicate whether the "orphan" is older or younger than 14.Orphans older than 14 could choose their own guardian.