For this jam I relied on the level loader from Maack's game template which takes care of loading (and reloading) level mostly for you, but a simple way to do it yourself would be to load the reload popup over the top of the current scene instead of it being its own separate scene. That way you have access to all the data in the scene, which should make it easy to find out which one you need to reload when the retry button is pressed.
As for the UI, you got that right in every level except the first, so just do it the way you did it in those levels :]