Everything would be terrible but some of what he describes is fantasy. Foe starters since we already know about what we have it will not require reinvention. A lot of electrical equipment will suvive, possibly whole power plants. DC electrical motors can be coverted to generate power so small 12v systems will proliferate.
Black powder is not hard to make and can be used in modern firearms and will be. Cases will be like gold though. Primers can be made from iodine and sugar. Nitrited cellulose will not have to be reinvented either. It will take time to rebuild and repopulate.
Lawlessness will tend to undermine the efforts of advancement but the surviving population will soak up every improvement.