regarding what you indicate:
1) you don't move the background to make an illusion of moving: must see if you are using a tiled background or sprite and the size of it must impact on performance...
1) the enemies you do not need to destroy them 1 second after start of layout. do it without a delay of one second, not problem
2) checks for an item in local storage will not cause any problem in CPU or GPU performance
3) lite tween gesture??? why gesture?
4) resizing an object with that plugin may not have also any impact on performance!