Thanks for taking such a thorough look at this NRKulus. I'm afraid the tritones don't bother me. I had fun with the text painting in this piece. There's nothing inherently wrong with a tritone, they just want to resolve, so having one at measure 13, on the word "desiderat" feels very appropriate. How better to express the verb "to desire" (some editions translate it as "to long," "to thirst," or "to pant") for water, than with chords that ache particularly harshly for a resolution? The main objection to them in choral music is that they can be hard for singers to hear in their heads, so sometimes a few people land on the wrong note, and the tuning falters. There's a tritone in, I want to say the Faure "Requiem"? that half the alto section chronically misses because they are leaping down to it and it feels so much more intuitive to leap to the tenor note. (Audiences don't notice, because the altos who get it wrong are still on a note in the chord). But in this case, it's a harmonic tritone, not a melodic one, and the notes are in the key already, and are approached by step, not by leap, so it should be solidly tuned without any problem.
At measure 40, the Bb in the alto is serving a similar purpose of text painting. The psalm text is all about the soul longing for God, so "anima mea," "my soul" crawls its way chromatically, hand-over-hand up the scale. The journey is supposed to be a struggle musically, since the text compares longing for God with a wild animal desperate for water. So we're crawling by half-steps.
The thinning of the texture at the top of page 5 was to another way to play with dynamics (four voices in harmony at forte is quieter than four voices in unison at forte because of the way the sound waves cancel each other out or augment each other).
At the end, I really like inverted chords, and since the text speaks of longing, but never of union with God being achieved, it felt appropriate to leave the audience hanging. We resolve a little, out of all that polyphony, we're at least quieting down into homophony and heading back home when we finally get to the text "ad te Deus" and find out what it is all this unquenchable desire has been about, but there's no promise that we've found God, so landing on an inverted chord, and then cutting the lights and saying, "that's all folks, show's over" felt fun to me.
Does it all work? I don't know. Your objections are certainly valid and well-reasoned and there may be better ways I could have supported my intentions. Shrug. I'll have to see if I can get someone to sing it and see how it sounds live. (: