Hi @pateceramics
A lovely piece, I also really like the text you have chosen.
The contrasts between solo, trio and tutti are really interesting to me, and I think you've done well to handle the various types of texture this throws up. I would maybe have liked a reprise of the solo or trio texture nearer to the end, as this could perhaps tie the structure of the work together nicely. Maybe even a reprise of the opening lines? Another thing: have you thought about the position of the solo voices? Are they all standing together in a group; in their normal places; spaced across the stage or even around the church/hall?
I particularly enjoyed the section from Bar 32-59 with the metric changes. It flowed very well despite the irregular phrase lengths and successfully followed the patterns of speech, thus it was very soulful!
After a quick glance, it looks okay. The hand that a pianist will play a particular line with is really due to hand shape, size, dominant hand etc. so is unique to each pianist! Unless it's an etude or similar where it really matters which hand plays what, us pianists will usually just play whatever feels comfortable to get the notes in. Is the part for rehearsal only? If so, I wouldn't worry about changing anything. EDIT: after actually looking at the score, I see that the piano is specified for rehearsal. You're fine to leave is as it is!
Well done, this is a beautiful example of choral music!