Dan, This is just a beautiful piece.
The simplicity of the song is it's strength, so don't muck around with it too much.
Just play it from time to time, even after you've moved on to the next songs and changes will organically present themselves.
I hope this isn't one of those songs that you put on the shelf and move on from.
I love what you've done here and as always your soulful delivery sell it. The chorus is off the charts and filled with heart break.
Bridges are so damn hard for me but I agree with Eddie just shuffle the chords around a bit.
I tried using Bb F Bb F and your ending four chords , E Am D7 G.

What a heart wrenching tune, my friend.