It’s gonna sound lame but get a 90s copy of the boy scout handbook and learn all the stuff in it by putting yourself in situations where you will use them. For things like tourniquets and other first aid, take a class. Don’t be afraid to update the methods by looking up stuff online.
If you’re not sure why I suggested this: bsa operated at one point as a pipeline into the military for children. The skillset it teaches is basically hobby infantry.