You probably know what your doing more than I do but ur object count is high and ur collision checks seem abnormally high for the game you are describing.
Also the fact the ur fps is dropping may indicate some object spawning or array growing out of control. Though I think that machine should be able to handle anything you throw at it. (Obviously Chrome these days is set to hardware accelerated as default but it is worth checking in advanced settings maybe it got unticked).
but before u start blaming ur code I would love to know...,
1) what FPS are you getting previewing with Edge on the surface book?
2) what fps are you getting from exported nwjs vs preview nwjs on the sb?
3) what fps are you getting on any other machine?
I ask because I have seen similar issues with previewing chrome and nwjs full screen on surface pro. But not when running exported. It may have something to do with vsync issues, or aggressive power saving (especially on the skylake models), while previewing chrome/nw.js on these specific ms surface pro/book devices.