1) You'll need CocoonJS Launcher 1.4.3 to test the physics works. It should already be available on Android, but I don't know when it'll come to iOS, hopefully soon. Workaround: use web-based physics.
2) The iOS retina display setting is ignored in CocoonJS. I cannot reproduce any difference in rendering after changing this setting, which makes sense, because the code ignores it in CocoonJS mode.