The series is long and boring precisely because it tried to address pretty much every claim like that at once. In this case GiveWell’s on record as not wanting their cost per life saved numbers to be held to the standard of “literally true” (one side of that disjunction) so I don’t see the point in going through that whole argument again.
Your perception that the EA community profits from the perception of utilitarianism is the opposite of the reality; utilitarianism is more likely to have a negative perception in popular and academic culture, and we have put nontrivial effort into arguing that EA is safe and obligatory for non-utilitarians. You're also ignoring the widely acknowledged academic literature on how axiology can differ from decision methods; sequence and cluster thinking are the latter.
I've talked with few people who seemed under the impression that the EA orgs making recommendations were performing some sort of quantitative optimization to maximize some sort of goodness metric, and used those recommendations on that basis, because they themselves accepted some form of normative utilitarianism.
Academia has influence on policymakers when it can help them achieve their goals, that doesn't mean it always has influence. There is a huge difference between the practical guidance given by regular IR scholars and groups such as FHI, and ivory tower moral philosophy which just tells people what moral beliefs they should have. The latter has no direct effect on government business, and probably very little indirect effect.
The QALY paradigm does not come from utilitarianism. It originated in economics and healthcare literature, to meet the goals of policymakers and funders who already had utilitarian-ish goals.
I agree with Keynes on this, you disagree, and neither of us has really offered much in the way of an argument or evidence, you've just asserted a contrary position.
The idea of making a compromise by coming up with a different version of utilitarianism is absurd. First, the vast majority of the human race does not care about moral theories, this is something that rarely makes a big dent in popular culture let alone the world of policymakers and strategic power. Second, it makes no sense to try to compromise with people by solving every moral issue under the sun when instead you could pursue the much less Sisyphean task of merely compromising on those things that actually matter for the dispute at hand. Finally, it's not clear if any of the disputes with North Korea can actually be cruxed to disagreements of moral theory.
The idea that compromising with North Korea is somehow neglected or unknown in the international relations and diplomacy communities is false. Compromise is ubiquitously recognized as an option in such discourse. And there are widely recognized barriers to it, which don't vanish just because you rephrase it in the language of utilitarianism and AGI.
So, no one should try this, it would be crazy to try, and besides we don't know whether it's possible because we haven't tried, and also competent people who know what they're doing are working on it already so we shouldn't reinvent the wheel? It doesn't seem like you tried to understand the argument before trying to criticize it, it seems like you're just throwing up a bunch of contradictory objections.
The most obvious way for EAs to fix the deterrence problem surrounding North Korea is to contribute to the mainstream discourse and efforts which already aim to improve the situation on the peninsula. While it's possible for alternative or backchannel efforts to be positive, they are far from being the "obvious" choice.
Backchannel diplomacy may be forbidden by the Logan Act, though it has not really been enforced in a long time.
The EA community currently lacks expertise and wisdom in international relations and diplomacy, and therefore does not currently have the ability to reliably improve these things on its own.
All these seem like straightforward objections to supporting things like GiveWell or the global development EA Fund (vs joining or supporting establishment aid orgs or states which have more competence in meddling in less powerful countries' internal affairs).
I know of one related effort: https://twitter.com/webdevMason/status/1234216664113135616
http://www.coepi.org/