All very interesting, what you wrote.
It seems to me, that Dougie MacLean is a very subtle person, and witnesses well, especially his own country, which they call Caledony.
Also he seems to me to have a patriotic vein on a very high but nevertheless positive ! level.

So if you want to know, what the lyrics mean you have to look here:
http://ads.ahds.ac.uk/catalogue/adsdata/arch-352-1/dissemination/pdf/vol_009/9_396_418.pdf.
Almost you will find there a well on the hill.
Are his words only a description of things his ancestors did or are they describing a special fact?

all the best Martin