John Butter was dismissed from his position as Clanranald's Factor on the Uist Estates in 1797, having lost the confidence of Clanranald XX's Tutors through financial mismanagement - among other things. His successor was Robert Brown, an Ayrshire-born lawyer. In 1811 Brown became Factor on the Lanarkshire and Arran estates of the Marquis of Douglas and Clydesdale and, on the Marquis becoming the 10th Duke of Hamilton, became Factor for all the Hamilton estates in 1819 - a position which he held until his death in 1855. Much of Brown's correspondence between 1797 and 1855 can be found today among the Archives of the Douglas-Hamilton family, Dukes of Hamilton and Brandon.
John Butter was in Benbecula in 1799, returning to the mainland in November of that year. In a letter from Hector Macdonald Buchanan, Clanranald's lawyer in Edinburgh, to Robert Brown later the same month, Buchanan writes that he has heard of Butter's arrival at Faskally but does "not imagine he will return in a hurry as his father is determined not to part with him until all his accounts are fairly given in and settled with the Tutors, for he will not again trust him out of his sight". Rightly or wrongly, I interpret this as implying that John was a son of Henry Butter of Faskally; whether or not he was a "lawful" son is open to question. You have a date of 1800 for John Scott Butter's death. John Butter, ex-Factor to Clanranald was alive and well in Edinburgh at the end of 1803. This information is taken from the Douglas-Hamilton Papers mentioned above - NRAS (National Register of Archives Scotland) reference 2177.