Well, to me, "crushed into instants" speaks to the how Nonmen perceive time, flattened out and non-linear, in a fashion. Like Auriga, says, I don't believe her face is literally crushed, more figuratively reduced. Her, face, rather than being the flowing beauty of the living, is a face reduced only to glimpses of it's former self. In other words, composed not in the now, but in memory, a collection of former instants. This speaks to a lack of self-ness, which is actually set up by the context, I think. Look at the whole sentence:
"Aisarinqu screams and Aisarinqu screams, again and again, not so much words as a storm of occasions, her delicate face crushed into instants and flayed across an age, for theirs had not been a happy union."
He, I think the crux is "not so much words as a storm of occasions" which is what "her delicate face crushed into instants and flayed across an age" is describing. So, she screams, not in the sense of sound, but with her face showing all the anguish of all the instants splayed across the ages of their unhappiness.
The big question isn't, for me, whether they killed their wives and daughters, because I think it's clear they did. The question is why? It wasn't just some male caprice it seems, because we see both Aisralu and Aisarinqu goading him to do it. In this sense, he seems reluctant and they seem determined on this outcome. This seems to point to the fact that whatever the condition facing the Nonmen women, it was untenable to both the women and the men.
Also, consider this line, "The white spark of some faraway light refracts in her tears, so that her contrition seems holy, and his embittered and profane." Both have contrition and considering Bakker's Cristian background, I think contrition here is the "the repentance of past sins during or after confession." Here, context to the Aisarinqu scene, it is an act of confession. He kills her, not for her sins, or his, but seemingly for both theirs.
Actually, now thinking on all this, what if you are right, with "Whatever gave them immortality must of drove their sexual craving crazy." That would go right back to my hypothesis that spawned this thread, that the Womb-Plague wasn't a weapon, per se, but was an enlistment. The Inchoroi gave them exactly what they had given themselves. The result? Wanton promiscuity. The women, rather than be solely objects to be used, ask, nah, perhaps demand, for death instead?
I'm not sure. Very interesting to think about though.