> I'm not a believer.

Yes, you are equally believer as I am, and everyone on the planet, scientific paper do not mean much (don't get me wrong continue reading), that was the thing I was trying to say, in papers, we have estimates and models, we do not know what will happen exactly in real events. (and that is the point if you are scared enough, you never attempt to attack your enemy) You asked me for an opinion, not the knowledge about the outcome - therefore, I believe that your estimate is low, and you believe my estimate is too high - but neither of us knows what will happen.

> There is no point: We agree on the facts

No, we have not. I just listed the initial blast losses and ask you bunch a of questions on what would follow, on which you have not gave any answers. Regarding the map, I know about it, and it is not a model. It is more of a joke. I can list all the things you need to include, and you build a model; again I do not know your field of work? What do you do?

Humanity can survive in multiple ways, and let say, if we build an artificial womb and save DNA samples, and then after waiting for 100000 years, AI restores humanity and the animal/bio world - is that a real survival?
Also, if we lose 99% and 1% continues, is that acceptable? For me, "The death of one man is a tragedy. The death of millions is a statistic." does not really work and it is not acceptable in any case or capacity.

How long will those need to get back on track? What about the amount of suffering they will go through? And after 10000 thousand years, will they repeat the same mistake, but this time with more powerful weapons? According to Mahabharata Indian legend, we already had a similar war with similar weapons a very long time ago, ok it is a story, not a real history as we know, it is more of as Science Fiction of old age in which weapons described are just amazing (self-navigated weapons, explosives, flying ships...)... anyhow I went sideways, I am trying to say the cycle of repetition is boring and at the end can get us extinct due to multiple other causes/agents.

Also while thinking about nuclear exchange we have not even touch that govs will not stop with nukes, there will be plenty of chemical and biological weapons exchange to finish what is left enhanced Ebola, black death and everything else you can and you cannot imagine currently at the military of the world disposal.

If humanity would drop to 100 million (1%) (population approximately 2000 years ago), how spread the population would be? How many gangs? How many tribal wars? Again, what with 450 nuclear power plants around the world? Surrounding of the Chernobyl will not be habitable for 20000 years. https://www.nationalgeographic.co.uk/environment/2019/05/che...

Now, in the time we need to recover, let say in all best conditions where people will not get hugely religious, and instead they turn to science, start learning as much as possible, that there will be no wars for resources, and gangs and criminals, that they will be very cooperative and not repeat same mistakes of the human nature as greed and lust for money, how many years would we need to recover from ashes and radioactive waste? 1000 years, 500, 100, 10 years? Damage would not be comparable to WW2 recovery, as scale of damage would be much bigger. And how would you organize society and make them do any work? How would you secure leader, aristocracy and politicians that caused this issue in the first place? Would they become primary target?

So, let say those 100 million left would need 100 years to recover, fairly optimistic time as nuclear winter would play a good part in the recovery time. During that recovery period, just a bit larger space rock can end the story, the same way like with the dinosaurs.
You could say that even now we do not have the technology, but current state + 50 years of new technology, we could have protection in the future.
But set back of just 100 years + same space rock few miles wide we would not have any protection, and it would be a game over.

All these scenario are hypothetical and we do not know really, but I would rather choose those probable scenarios that will increase our chance. As I know one thing for certain, I do not know where you live and what are your survival skills, but here in London my survival chances in the case of event are equal to zero and I have to admit I love internet even when we do not agree on things we do not have any influence whatsoever. :)