I believe Sarah (Boone) Humphrey is correctly associated as the daughter of John Boon (Boone-1367) and Elizabeth Alford (Alford-1000).
My reading of the Find-A-Grave entry is that the claim that John (Boone-1367) was the nephew of Daniel Boone has not been proven, and is based solely on the statement in his pension application that refers to "uncle Daniel Boon" - his children do not seem to be the issue, but HIS parentage. If there is unlinking needed I would suggest it is John (Boone-1367) from Israel Boone (Boone-107) and Mary Carter (Carter-7252)
See also John Boone in the 'undetermined connections' (p. 492) in Spraker's The Boone Family
While there may have been further research done, the above work (p.38) also indicates that the wife of Israel Boone (Boone-107) was unknown. The only Mary Carter mentioned in the book is in a footnote (p.61) as a possible wife of Jonathon Boone, one of Israel's siblings.