Human extinction is neither near nor particularly inevitable. A few small groups (rich people) will always find a way to survive, most likely by exploiting those less fortunate. It's just that a lot of people are gonna die while we turn our planet into a living hell by extincting all the other species.

Stages. Long, awful stages.

Anything that helps, helps, as in "it can always get worse".

I will something more akin to 'Into the Badlands'.

Wealthy people will exploit the poorer more and more until there is nothing left but indentured servitude for the resources you need to stay alive.