Well I cannot help you with the fix of the crashes, maybe those devices currently have issues with the Crosswalk build.
(You can be sure if the issue comes from Intel's Crosswalk build they will fix it shortly.)
Talking about the Crosswalk build, since Crosswalk is using chromium (a kinda browser) to build and play your app, the size of your game itself will be big.
Your app can be as simple as you want, the exported C2 game at itself is always lightweight but when exporting with Crosswalk it will get bigger.
Perhaps you can use Phonegap or depreciated exporters for sure, but currently Crosswalk export has the best performance and is supported by the most Android devices.