Susan,
You may well be right regarding the Douglas Tragedy influence. It would be worth discussing this with a local expert if we could find one. Ronnie Clarke is not that far away in the Kircudbright area. The Hornel might be able to throw some light on this, perhaps in the Macmath papers.

I'll have another look at the chronology and see where broadsides come into it.

'That's important if you're trying to see where printed texts may have influenced subsequent versions.' True. Does that mean Kinloch's version published in 1827 was the earliest published? I can't find any broadside printings earlier than about the 1840s. The only one with a definite date on is Glasgow Poet's Box 1852. There is a broadside in Harvard printed in Glasgow (listed in Welsh and Tillinghast 1368) which could be Robertson which would take it back to about 1800. The broadsides all seem to have the 10 or 11 verses of the burlesque.