The problem is that with 30 fps, when falls the "Sprite 9" red, falls throttled back and it looks bad.
Try to remove WebGL and works somewhat better, with 9 physical objects I have now 45 fps, but I can not put more objects because the game becomes unplayable
Try "Physics - basics" of examples of construct 2 on my iphone 4 and it works quite well and has plenty of physical objects. My head hurts with all this.