Aha, it works now. I'm not certain but I think I might not have noticed before that you have to click "save" to make the settings work. On my screen that involves scrolling down. You might move the "save" button to the top of the settings screen to make it more obvious, and possibly call it "apply" rather than "save".
I do remember that the new settings persisted in the settings screen after switching to and from the main screen, and that was part of the puzzle.