I've had fun with your game!
Unfortunately, I had to use a buggy work-around in the room with Dungeon Key I in order to progress, I was able to use the newest version of the game to update the map such I get the key itself but you can't return to the heal/save room. There's currently a buggy work around to progress:
Another minor bug related to the same room, when you enter it for the first time to attempt to trigger the cut-scene so you can do the mini-boss rush, you have to approach the tile from below to trigger it; this means you can miss the trigger for it, go get the key, THEN contribute Vivi to the room in order to get out.
I think the intended sequence is to enter the room for the first time, Have Vivi Stay, then revisit the room for the key later and be able to exit the room. Hope that made sense and helps.