You obviously are a pro! Thanks for sharing this beautiful piece. I have a few questions though:
1. Would this fall under 'incidental music'?
2. The half-diminished seventh chord in bar 19 sounds a bit 'daring' to my amateur's ears. Don't listen to me though!
3. Is the tenor part transposed up an octave (it's in the treble clef)?. Some parts end up crossing over the soprano's line.
4. The soprano and tenor parts are pretty high in register. You must have a professional choir in mind? Or is this commonplace?
I'd love to write choral music as well, but as you said, the realization is tricky; mock-ups usually end up being instrumental music. BUT have you seen this?
East West Samples - Quantum Leap Symphonic Choirs
It costs a great deal of dough but boy what an empowerment it would be! If you ever decide to shell out for it, please do post the results!