Him enduring more than one shot is stated by Hawkins who was looking at the scene, and he was mentioned after Luffy defeat (mentioning him as another CoC user)
If anything it’s better hype for Killer.
Nothing that Oda couldn't explain with his permanence for 2 years in the NW or that he discovered it during his invasion of WCI
With Law, at least, Oda have us hints that he had something to do with the D plot well before we found out he was one, when he said “the D’s will bring about a storm” after Marineford. Kid has nothing like that. Just look at Wano- Law went looking for Poneglyphs in Onigashima. Kid’s never even said the word Poneglyph.
Bounties are given by the events Navy assists to or is informed about. Navy was not present in WCI so the bounty was given by Morgan information (which pushed in calling him the 5th Emperor of the Sea)
Kidd actions in WCI didn't merge outside of Totland
Kidd actions in WCI didn't merge outside of Totland