Forgive me but the Angus Campbell I mentioned was born about 1770, is a famous poet in the area, writing both a praise poem and a lament for the famous Flora MacDonald's nephew Capt Angus MacDonald IV of Milton, who drowned in Loch Eynort in 1806. He was still in Aird after 1841 and died there, being succeeded by his sons. What I was suggesting was that Angus' family, which had been in Benbecula for at least three generations, so back to not long after 1700, and was the only family of the name in Benbecula, might just be the origin of the man you are seeking. It carried the names you mention, admittedly fairly common, and the Bard Sgallach, as well as a collected poet who figures in the MacDonald collection, was a tailor about whom there are still extant tales so that, if anything, though short of the specificity you are looking for, also supports my suggestion.