Isaac Fisher Apgar is documented in the Apgar Family genealogy. According to Volume I, page 288 of the book 'Johannes Peter Apgard and his descendants' published by the Apgar Family Association, "Isaac was a farmer and a carpenter.They lived in Bridgewater TWP, Somerset County, NJ.They are buried in the cemetery of the Hilltop Presbyterian Church in the town of Mendham, NJ."
Isaac was married to Elizabeth Sutton (1848-1936) on Dec 16, 1866, location unknown.Isaac was a son of Conrad Apgar Jr and Sarah Hoffman and grandson of Conrad Apgar and Charity Sutton, daughter of John and Elizabeth Aubel Sutton.
ps. Great job with the Hunterdon County abstracts.I've found a lot of useful data in them.