Thanks for the feedback, Lyndon and Lynn! Good points all round. I definitely work out something better with a rhyme in that last stanza. In progress. 🙂
I think in this context that chord is functionally just a chromatic submediant (or bVI) expansion of the subdominant (Eb) harmony. It isn’t behaving as a Neapolitan ordinarily would, which would be leading directly to dominant harmony (even though it is in the typical inversion with the typical doubling for one). I’ve a mind to see what happens if I change the ending so that it does behave more as a normal Neapolitan. But then I risk losing the climax of the harmony and melody on the word “Jesus”, which I rather like.
We’ll see. I definitely want to improve that last stanza of text.