The Home Doctor - Practical Medicine for Every Household - is a 304 page doctor written and approved guide on how to manage most health situations when help is not on the way.
https://www.digistore24.com/redir/394659/Bipin9764/
If you want to see what happens when things go south, all you have to do is look at Venezuela: no electricity, no running water, no law, no antibiotics, no painkillers, no anesthetics, no insulin or other important things.

But if you want to find out how you can still manage in a situation like this, you must also look to Venezuela and learn the ingenious ways they developed to cope.
https://www.digistore24.com/redir/394659/Bipin9764/