In my experience, blocking was more effective against rapid shots, while swinging your Keyblade was more effective against spread shots. By the way, I think Sora might work as a skin for Ryu, but he'd probably need all custom sprites.
I distinctly remember deflecting ice shots back at him. Ah whatever, you're probably the best source for KH knowledge anyway, I haven't played the games in years.
I've tried more than once to use CoM's sprites, but they're always too big. So you're 100% correct on this. Might've been how you did it I guess? Myself and everyone else I know who's done that fight found it easier to just block them back, but you never know. Maybe you're just really good at deflecting with attacks.