Marking a Hymn as a Favorite is already possible. Just touch the heart icon on the song and you'll find it in the My Favorites section. The multiple lists idea is interesting. Please post that as a separate topic as I'm going to close this "Favorites" one. 

This was fixed in last update, v. 4.2.1

At this point, we are not seeing any evidence in our crash logging / error reporting of a widespread issue affecting multiple users. In your case, we recommend uninstalling and reinstalling the app on your device.

We adjusted the weighting of search results to provide more expected results. This is live now.

Do you also get a duplicate notification for new Silver Linings?

This is helpful. Can you also post screenshots showing your notification settings and the time setting for the prayer notification?

Thanks for reporting this. Looks like we need to adjust the weighting of these type of search results to produce a more logical ordering.