Fourth scale degree diminished chord in Have yourself a merry little Christmas

So in the Frank Sinatra recording of Have yourself a merry little Christmas at 2:03, the vocal arrangement (as far as I can tell) goes:

Key of Ab

Here we are as in olden days

Dbmaj7 Dbdim7 Cm7

Happy golden days of yore

Cbdim7 Bbm7 Eb7 Abmaj7

Faithful friends who are dear to us

Dmb5b7 G7b9b13 Cm

Gather near to us once more

Eb/Bb Bb Ebsus7 Eb7

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So my first question is, do I have the chords right? (I realise there's a few suspensions missing)

Second question: what would we call the two fully diminished chords?

I guess the Cbdim7 is a passing diminished chord, but what about the Dbdim7? None of the online resources I've found list IVmaj7->IVdim7->iiim7 as a possible usage of passing diminished chords, so what gives? Am I just overthinking this?

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