If a full scale nuclear exchange occurs, the probability of death does not come mostly from the nuclear blasts themselves, or even the nuclear fallout from those blasts. Rather it comes from the breakdown of critical infrastructure needed to produce food for a population. If every major city is destroyed at once, you almost certainly won’t survive a year even if you are nowhere near a blast zone. Your only chance is if you already have the means to farm sustainably without buying manufactured goods. Even most farmers these days can’t do this, at least not easily, because they need gas. Even if you are one of the few in a position to survive in this way, everyone who can’t will be gunning for you, because they don’t want to starve.
I don’t want to live through nuclear war. The worst parts have nothing to do with the explosions. The worst part comes after. It will essentially be a siege, everywhere in the world at once. People will eat each other.
As a first approximation, if the food production falls to a level of X% of the required calories for the population, your probability of surviving is roughly X%.
I mean, today food production is significantly more than 100% of the required calories for the population and many people are still food insecure