The thing really jumping out at me is that the gun in those two photos from NYCC and the ones in the stills just clearly are full stop not the same gun? Given the wear and tear on it, perhaps he starts with the first gun,and then gets the new one when Broom presents it to him in the film?
As for the film, I have a lot of fanboy nitpicks about it, his hairline being way too high on his head, Daimio's transformed self being kind of amusingly small compared to what he is in the comics (Not to mention we never see he and Hellboy actually meet in the comics), the fact that Broom seems to have been remade into a much gruffer sort of character, etc. And I dont love the new arm, it's way less interesting visually than the old one, not to mention it almost looks like metal compared to the stonework and engraved look from before. That said, I'm gonna see it opening weekend, cuz I'm a huge Hellboy fan and want it to be good. Who knows, it might be great.