The marriage between James IV and Margaret Tudor was in 1503 by which time Henry VII had been around long enough to be established whereas in 1488 James' own father (James III)had been killed by his own nobles. Not really a sign of a stable family rule. Henry had established himself at Stoke Field the year before (1487).
If the aim of the invasion was to pull back the English from France then it failed.
I see the old boggy ground argument coming out again. Branxton Edge is an escarpment or ridge so I don't see it as "enclosed" or "claustrophobic".
While the Schilron was defensive the Scots in 1513 had Swiss style pikes typically used in the attack.
The idea of (Italian) Renaissance Warfare being a game of capturing knights as being the norm may or may not be true, but the Wars of the Roses practicised the exact opposite and Border Warfare was not of this jolly game type.