You left out an important physical factor which changes everything; energy, and where it comes from. We have reached the point globally where the energy which can be extracted from Earth without shutting down the energy of the environment has come to an end. The environment is already starting to shut down, hence the worsening storms and heatwave extremes.
Further energy extraction despite this, only shuts down the environment more rapidly. This is a non negotiable, non linear physical process that we can't get round.
Either we change energy source from energy extracted from Earth, to energy donated from space, or we radically cull our population to cut our rate of extraction, to allow us to do it a little longer, perhaps until fusion might be achieved.
Currently we seem to be on the path to doing the latter.
This is a much different situation than ever existed before, all previous estimates of the after effects of a nuclear war no longer apply.
This time the nuclear war, if it happens, will occur in the middle of the climate tipping point.
There would be no surving that, it has to be the end for all living things.