What does the Mongoose say to Oscar at the canefield?Near the end of the novel, Oscar Wao is on the brink of death, and he sees the mongoose, and...

Earlier the three dashes are used by Oscar to stand for words he dare not say, lest he be cursed by the fuku: "I Love You."

I think the Mongoose is saying the same thing.  The Mongoose sees Oscar as a martyr for a higher love to spite the fuku.  The Mongoose (a mythological sign of altruism) is saying that it loves Oscar for dying for such a noble cause, not for selfish reasons.

The faceless men are symbols of the Secret Police, Trujullo's minions.  If Trujillo is Sauran, then the faceless men are like the Ring Wraiths from The Lord of the Rings, phantoms who steal and kill under cover of night.  They carry out the Dark Lord's evil.