This looks really great! Do you offer an api as well? I'm part of the team behind https://cyclema.ps and we'd love to see if we could incorporate this as a backend.
The backend at this point is just Graphhopper so I think it would make more sense to use it directly and customize it based on your needs: https://github.com/graphhopper/graphhopper
Looks really nice - congrats on the app :). I can't test it since I don't use iOS. But if you ever make an android or web browser version - happy to play :)
As a cyclist, I would never plan routes on a tiny phone screen with a crappy UI. I would always plan on a computer and then use the phone to keep me on track.