Help for writing an app (running zones using Karvonnen method)

Then how about leaving it as is, renaming to Run+, specifying only Bangle 2 in metadata and just wait for somebody to implement additional screens there before thinking about how to split them out? That could also be a base to try out minimizing RAM usage by loading/unloading the screens inside the app to make it work on Bangle 1.
Getting exstats to store on exit is probably useful anyway, since not being able to switch apps on a longer activity like biking is a bit limiting currently.