I liked this as well. I'm very familiar with the original version, and I felt this might have been a little bit too hurried in tempo. I would love to hear this swell up and romanticized. This is a dramatic prayer, not to be hurried.
Also, the addition of major chords felt a little off to me . I love that you tried experimenting with the prayer, but I felt it should have STAYED with using the off scale it was written in or at least have gone to a minor key at the end. The reason why I say this is because when you have a chant, such as this, it normally stays in key and very drone. I felt your soprano part should have entered a BIT earlier as well, but as you have said in your description, you were just messing around with this.
And please, don't take this review as me trying to say that you did absolutely terrible because that is not the case. I loved this one very much. I just hear different things going for this.
Overall, very very nice. Theoretically and aurally, everything fits and sounds good.