Writing chords across the line is easier to write, and to read. Then your Dm7 chords are written x57565 and xx0211. Note that the second is just the first with the top A note removed: x5756x. The version without the top A works better because your chord sequence has all the chords with F as the top note, right? For a bit more interest in the chords, you can play the Bbm (xxx321) as a C phrygian chord: x3x321. Either way, the chord is playing the role of the dominant.