LOW_MEMORY error when loading app

Is there a way to split the app on the Bangle itself, using different "files" in storage?

Yes - this might help :) http://www.espruino.com/Modules#from-sto­rage

Depending on the images, they may be eating up a bunch of space. You can store those in storage and load them as needed. A bit like is done for https://github.com/espruino/BangleApps/t­ree/master/apps/animals

as I have my own pipeline to bundle and minify my app

I'm not sure IDE minification will have much effect then. The code you uploaded definitely looked like minification could help it significantly though.

splitting my app in chunks when writing it in storage is not a good idea

... for now :) At some point I think I will have to add the ability to execute code from Storage, so when that happens it'll be fine.

I'll also be extending the IDE and command-line tools to do the chunking automatically though, so that should help you out