Going over the list:  I'd limit 'errata' to math calculation errors (CR not matching Prof. bonus is excluded), the XP variance, and the missing DC on Cloud Giant.
Basing the proficiency on the CR is not a hard rule.  I wouldn't include the 'errors' that refer to background math or general rules (large creature do double).
The formatting, spelling, and redundant 'damage' entries I'd correct in the next printing but not include in the player facing Errata.
For AL play, I'd consider changing CR values on the Giant Poisonous Snake and the Pixie - depending on how common the 'Pixiemancer' and 'Beastmaster with King Cobra' builds are in AL play.
Short List:
Change the resistance to weapon damage types wording to apply to all attacks - not just weapons.
HP
Horned Devil	178 (17d10 + 55)	148 (17d10 + 55)
XP for CR
Ancient Black Dragon	27,500	33,000
Ancient Blue Dragon	32,500	50,000
Ancient Green Dragon	30,000	41,000
Ancient Red Dragon	36,500	62,000
Ancient White Dragon	24,500	25,000
Ancient Brass Dragon	24,500	25,000
Ancient Bronze Dragon	30,000	41,000
Ancient Copper Dragon	27,500	33,000
Ancient Gold Dragon	36,500	62,000
Ancient Silver Dragon	32,500	50,000
Empyrean	32,500	50,000
Adult Brass Dragon	Breath Weapons (Fire Breath)	49 (13d6)	45 (13d6)
Ankheg	Bite	9 (2d6 + 3)	10 (2d6 + 3)
Missing DC
Cloud Giant	--	15