Sorry but this lags also on android high end devices and a game like this should really run smooth even on an old iphone.
Here are some tips.
1) (Most important and probably the real cause of your lags) NEVER use text objects updated every tick with WEBGL turned on. Remove them and let me know if you're gaining some performance.
2) If you want to test on iOS don't use chrome. Chrome for iOs is a skinned version of safari. Try the CocoonJS launcher instead or an exported ejecta build.
3) If you're targeting iOs, even if you're using CocoonJS or Ejecta use Canvas2D instead of WebGL. I've never seen a game run better with WebGL turned on on iOs. The situation will revert only when iOs8 will be out since this update will contain (finally) a proper native WebGL support and a modern JS interpreter.