about the text box in the corner, that nostalgia is a great reason to not change it. the main problem I had with it is that it’s easy to miss if my focus is elsewhere. you could consider showing a little exclamation symbol near the player character as a clue for when the text box appears, to make sure players don’t miss it. it’s not strictly necessary though, so do what you feel like.
for the mushroom puzzle, that could be solved by only passing the check if you have 3 correct and 0 incorrect. I don’t get your point about “forcing full interaction” — seems a bit contrived to me. but that’s sometimes the charm with games like this, so again, do what you feel like!