Hi! Glad to read your detailed reply! First of all, good luck with development! Sincerely hope you can achive all your goals and make the game you want!
Thought about gameplay and want to share an idea with you, maybe replaying day will lose it's progress, something like Groundhog day, and to complete you need to find a strategy to help them all in one try. It'll still keep that mechanic of helping each day, but will involve more thought process, cause you need to do everything at right time with right tool in one run.
But i see, that you try to make game reachable for non-gamers, and that's great goal! In that case you really want to make game as accessible as possible, maybe diegetic signs is great way, but you sure need some UI elements, something like which button to press, just to keep non-gamer in an environment where he understands what everything works.
Also, loved an idea that there will be funny animated scenes when failing to use item!
Again, good luck with your work, surely will follow your game!