Explanation on song based in mode/major key.

Ok the background on this is I am writing a song, it is fine sounding but there are a few things that wouldn't add up in the creation of the song and I was wondering if any advanced guitarists could have input. The song is based on a D phrygian mode. D phrygian is the Key of Bb major beginning on the major third of Bbmajor. The verse and intro are definately D phrygian based, but when I go into the chorus, it is moreso based on Bb major, using a Bb, C, D, Bb, F, A7 progression. This is really nice with phrasing. Later I go into a bridge made of a basic sequence of D, G, Eb, C, Bb, A. Now I really tried to add some chord identity to this part of the song, and this is where I need help. I took the key this piece is in Bb major. And according to the simple laws of chords in major keys, it should have sounded very nice to have Dm, Gm, EbM, Cm, BbM, ADim. When I did this it did not work out, just plainly to the ear it sounds off. I believe it is because i was working part of the song in D phrygian which should have a minor sound but the Dm won't fit. But I find a major won't fit well either because it doesn't go with the key of Bbmajor, so I am looking for some chord that will satisfy both the mode and the Scale. This would be helpful because a fifth chord is all I have found so far but i want something better. I also have this issue while writing in Dorian.