White spaces at the edge of the game are due to aspect ratios. Currently we don't support letterbox on CocoonJS or directCanvas so you need to handle this yourself. So for now the white spaces aren't a bug, it's just showing more of your layout than you intended. More info in supporting multiple screen sizes.
30 FPS is a good result for a mobile game - some mobile browsers struggle to get 10 FPS.
If you can demonstrate any specific problems with minimal .capx projects, we can possibly fix them. Unfortunately with the information you've provided we cannot fix any of those other issues.