@Vinians I took a look at your .capx, and I fixed some things so it will work in full screen. But there were some things I couldn't fix because I only know English.
The things I couldn't fix are:
The Fundo1 background image I got it to center on the Tela1, and Tela2 layouts but some place in your code something is making it enlarge, and repeat off to the left. If you can find what is causing this I would just disable it.
On your evGameOver event sheet I commented that you should just disable your sprites movements, and set them to a set position. this might help with your games FPS.
Here is your .capx:https://dl.dropbox.com/u/43763487/TiroAoAlvo.capx
Also to make your game run faster you might want to use System EveryX seconds and set it to 1 instead of using system every tick. And because your game uses the physics behavior you might want to use CocoonJS instead of Phonegap it will run much faster.