Yup, that's fixed it. Thanks. Haven't found the secrets yet, but the game is beatable now.
Don't know if the guns are really adding much. I pretty much never had to time any of them. Not sure if that was deliberate or not, since I know there is a slight gap in their firing after a fairly long delay. The only one that gave me any trouble at all was the one beside the double-jump, and that one stopped being a problem when I finally started thinking to make sure the double-jump fired before moving right.
Otherwise, a lot of the timing actually feels pretty solid!