I'll work backwards - mostly to address your miscategorizations of my posts - but this is the most glaring anyways:
Most here get it - I'm hardly in the minority (not that an appeal to the majority is important, but it just goes to show). I sometimes wonder if some have a 'better' ability to be contrarian and argumentative than to read the actual story, but I'm sure you must think the same of me.
Anyways - Yas gave WW the ability to do EXACTLY what he promised to NN. You know, to be 'loyal' as I believe that is your choice of words.
WW could have worked to save his kids, be their father and in their life, AND the dogkin from being slaughtered/used/enslaved. Oh, as well as all the other animal-kin Yas could scurry up.
Maybe he (WW) was OK with being a yes-man/dog as a slave of types, but they never got an opinion poll unless I missed it. (Not NN, not Yas, not WW's kids, and none of the animal-kin - as if it weren't obvious enough)
Part of being 'loyal' is being a father - a present father (and um, PROTECTING them), and keeping your word to your spouse/baby momma. WW failed at both spectacularly.
Let's also not forget that he only laid with NN in the first place because he was ordered to sire a child. And she, being a prisoner, complied. Not that she had much choice. Just because she was a well-kept prisoner and WW was a stud she was attracted to doesn't mean she had full ability to consent. There were obvious power dynamics and coercion going on. So, WW... what a stud. In the real world, this would be a technical rape. But I digress...
Then, post-coitus, the LEAST he could do is make a promise to NN and actually follow up with it. Spoiler: he didn't even try. Such a stud!
THEN - because this chapter didn't happen in a vacuum and one must consider the previous events/chapters as well - Yas lets WW know that his kids will be unwilling tools for Rei. He even knew the ones sent to the outskirts would be taken out. WW's reaction was 'meh'
Even upon hearing that NN was on board, WW wasn't moved. Yas brought up that he had PROMISED her.
He didn't scheme AGAINST WW, he schemed FOR him - and he told him exactly how it would play out - and when - when the new child (Paul) is taken to the mothership, it will be time. He absolutely didn't do anything that should have been surprising, and worked hard to make it work for everyone involved - from WW down to the dogkin and the kids in between - NN included.
Yas asks NN if she is SURE - she says yes and to proceed. To protect her children. She counted on and relied on WW to keep his word. She's JUST as integral as Yas in all this.
Yas then 'told on WW' which was of course fake, as his goal was to create a scenario that doesn't illicit a response from the FH (that backfired, but at least the intent counts) that also gets all the dogkin together (to be able to escape).
WW *STILL* doesn't leave even though Yas and NN's plan was telegraphed well in advance. He acts surprised, which also makes him stupid on top of everything.
Rei arrives with his dead-ass girl, and all WW can talk about is how loyal he is lol.
Only, just seconds ago Yas pointedly said: "You would rather betray your own lover // to keep your allegiance towards that damned master of yours?!!" - emphasis added. The one that can't stop talking about himself and what he wants - screw those in his circle - is none other than WW. The one that betrayed those close to him, WW. Hardly 'loyal' - and I'm not sure exactly what you mean by 'magnanimous' in regards to WW. He didn't even have to die for them had he actually worked with his best friend and wife. AKA, stupid.
WW's last-minute (AFTER he had already been burned) jump on a grenade is a little bit too-little-too-late.
TLDR, the rape-on-command chad that is WW is unreliable, betrayed his wifey and her trust in him (and his promise to her to protec their fucking kids for crying out loud), his people, and his kids to being used as slaves and/or killed on a whim. It is actually WW that is the selfish person in all this, not so much Yas, who actually worked to help WW *and his people/kids/girl* - it was WW that could only talk about what HE wanted, who didn't consider the life others would have based on his actions/inaction.
You have it exactly backwards.