muraria, silly me thinking it would not be fair for words to go through walls (if indeed I have the (4,5) you're referring to). Not the best ending for an otherwise perfectly cromulent puzzle, I think.
Well, Ithink I have finished this but am left with a sense of 'Oh, is that it?' so who knows? Perhaps I'm missing something, but it feels a bit ho hum at the end.
I'm still confused by the endgame. I have a couple of words (4, 5) across the lower rooms. Not sure if they're right. No idea about the key. Does it make a four letter word?