Sorry for response so late.
# You can run TestCpp -> Performance Test, and add the number of sprites and see if FPS fit your requirement on Galaxy S2. AFAIK, 1000 sprites using CCSpriteBatchNode works very well.
# Cocos2d-x is very easy to install, it’s only a framework. But the android ndk + sdk environment installation is a bit tricky for beginners, especially on windows. I can finish android sdk + ndk installation in 30 minutes on mac osx, so it depends on your experiences with android
# Please refer to
CCTextureCache::removeUnusedTextures(). Don’t worry about the power of cocos2d, it has been proved by lots of top grossing games.