Yeah they won't break a sweat and are stronger than them, also don't forget the fact that Donald at least heals you XD, or in another case you've either used cure or a potion and then that duck finally decides to heal you (~>_<~).
Yup. Game play and cutscenes are different
Sora would get owned if he was against Ventus. But as of present? Riku and Sora are getting stronger and learning how to use the keyblade better under Yen Sid.
As far as I understand, they were still weaker than they were by the end of the second numbered game. However, I think you're right in that they are getting stronger during and after the events of 3D. At the very least, I expect Riku to be at least somewhat close to their level now.