Lots of questions

There's a composition competition taking place in Santiago de Chile, my city. The requirements are that it has to be a piece between 8 and 12 minutes long for soprano, clarinet, violin, cello and piano. Basically, Pierrot Lunaire without flute or Quatuor pour la fin du temps with added soprano.
I decided to participate, since I think it is possible for me to write a piece for this ensemble, and also because I've always wanted to participate in some competition in my city.
I chose the following text, which is in Mapudungun, one of the native languages of Chile, which I unfortunately don't speak but find extremely beautiful. The poet is Leonel Lienlaf. A translation follows the original text, I apologize if it's not so poetic, but I tried to get more the meaning than the poetry, also I'm translating from a translation (from Spanish to English), not from the original.

Ka Feipituan

Ka feipituan ñi mongelen,
ñi ülkantumeken
kachill kiñe trayen.

Ramtuafin ti antü
chew küpaimi?
rupale tripantu
ka feipituan.

Alepue mapu küpan pian
amulen, amulen
alüpu puan
doy ayeple wanglen.

I will repeat

I will repeat that I am alive
that I am singing
close to a spring
spring of blood.

I will ask the sun
where does it come from
and if the years go by
I will repeat the same thing.

I come from the lands of Alepue, I will say
I move forward, I move forward
I want to go very far
beyond the threshold of the stars.

I've been trying to write music to it for already two weeks, but nothing good has come out yet. I have lots of questions to think about.

The text is fairly long, how to maintain interest with such a long text during such a long period of time (10 minutes)?
How to structure the piece?
Would repetition be of any help here?
How to create tension without making the soprano scream or having a Chopin-like passage in the piano?
What chords to use? How to obtain the chords without having to resort to tonal stuff? (No, I don't want this piece to be tonal in the XIX century sense of the word).

I have many more questions, but these are the more basic ones, which I could summarize in "how do I write this piece?".
I have been listening to a lot of Messiaen and like very much how he works with very simple structures that organize very complex material. I relate very much to the ideas of order and simplicity that I perceive in his work. I think I can go more into that...

Yeah, there's a lot of confusion going on, I hope I can get things clearer and clearer with this. For now, I leave you with some real Mapuche music.

Grupo Araucanía - Wenceslao Coilla