Vincent, I too can really appreciate this piece!
After listening to it, I’d say my thoughts line up much with Lynn’s.
Some additional thoughts: Going from predominant harmony in measure 4 to dominant in measure 5 and then back to predominant in measure 6 felt a bit awkward to me. Similarly, going directly into predominant in measure 13 after closing out the previous measure with the vi tonic substitute had a similar effect on me. I think opening measure 13 with tonic harmony would be more effective.
On measure 15, I do like that it helps bring the voices together into measure 16 but my ear wishes to hear the V instead of vii.