That extra bit doesn't belong to Willie MacIntosh (Auchindoun) at all, but was grafted onto it by some band called Gallowglass, of whom I know nothing (there seem to have been several groups or bands by that name). According to the Cantaria website, they got it off a record made by another obscure group, The Wallace Clan. No useful information is given, but the lyric is quoted. It looks to be a children's song, and has a different tune. The Burning of Auchindoun tune was popularised by Ewan MacColl, who reckoned to have got it from his father, William Miller.

Not Gaelic as such, I think, but Gaelic-style vocables (meaningless syllables used in singing).

"Crawing" is the same word as "crowing".