The problem with making a harmonic analysis of this is that the lowest notes aren't really a bass line, they are the melody.
As such, writing chords like C/E, Am/E, etc is "correct" in a literal sense, but the "/E" doesn't really imply a conventional harmonic function of that note as the bass of the chord.
In bar 3, there is no real functional difference in the harmony between F6 Fm6 or Dm7 Dm7b5 - personally I would probably call them F chords, because to my ears that's what the sound like.
IN bar 14 your "apart from chromatic voice leading might imply you think "chords" take precedence over "voice leading" - that is often not the case! I would be inclined to call the chords Gdim7 G7, again ignoring the harmonic function of the bass note. It certainly doesn't make any harmonic sense to call the first chord Bbdim7 here, just because Bb happens to be the lowest note.
In the penultimate bar, if you call the chord Fm6 chord you do have a conventional (plagal, iv-I) cadence. Naming it Dm7b5/C because the "pseudo-bass but really melody" note happens to be C confuses the issue, I think.