Nothing would surprise me about the MacDonalds. Especially what they sell in their outlets as food wrapped in cotton wool. Lord MacDonald of Sleat was the one who lived the life of a lord in the casinos of France and Italy and put the rents up every year of his tenants at Braes on the Isle of Skye.
However, wiki seems to have a different version of their origins. Possible male line from Ireland and female line from Norway via Orkney.
https://en.wikipedia.org/wiki/Clan_Donald
Historically the MacDonalds saw themselves as descended from the High Kings of Ireland, but then they all did. Although they were the Lords of the Isles for a long time until the king in Edinburgh decided to rein them in.
It's interesting to visit Skye and compare the MacDonalds from old portraits at their visitor centre, which is an excellent museum and well worth a visit, with the portraits of the MacLeods at Dunvegan castle.
The MacDonalds seem to be very fair and really do have that air of 'gentlemen', that kind of public schoolboy look, blue eyed and innocent.
The MacLeods are a swarthy black looking bunch in spite of their claims to be Norwegian.
One of the problems with Scottish clans is that not everyone in the clan was actually related to the clan chief. The chief and his family were a kind of overlord or 'godfather' who protected all those who swore allegiance to him. Of course that meant that the clansmen had to rise up on his side when needed. But having the same name was a way of saying that they were all in the same gang. Conversely people from differently named clans may have been related to the other clan. People tended to keep their own knowledge of their origins through reciting a list of their fathers, grandfathers etc. So the well known Glencoe Macdonald was known as MacIain rather than MacDonald.
As regards the language, I was told many years ago by a Tunisian that Arabic puts the verb before the noun or pronoun. That's what Gaelic does. But then Gaelic uses continuous tenses like English, has no infinitive like English.
The Irish legends tell of ancestors coming from Troy, Egypt etc. Which puts legend at odds with Barry Cunliffe. Unless there were incursions from elsewhere which added to an already permanent population. In these circumstances perhaps Gaelic developed as a 'creole' language, a trading language understandable to populations all along the seaboard as Cunliffe claims?