Chord names; Gm in Dmaj`?

Hi,

Could anyone help me naming those chords in the piano score of Elvis´ Surrender?

The original key from this:

https://www.youtube.com/watch?v=bGYjWfp3aQI

track must be, so I heard it, Eb minor. I pitched it down one halftone to Dm.

The chorus (bar 25) is in D major.

What about those chords I already named. Are they okay and what about "this thing" in bar 48?

I can´t even imagine what this could be. Perhaps anyone could solve my obvious problem and perhaps explain the theoretical, progression"" thing to me.

I´ll attach the piano score.

Thanks