The poor outside of cities who are not subsistence farmers will be in an equally bad spot. Modern farming has not been an independent activity that can be pursued without external inputs for several hundred years. No fertilizers, no hybrid seed shops, no machinery repair, no fuel or electricity means no farm. Rural residents who can hunt might last a bit longer, but I would put my money on a suburban hipster with an organic garden and chicken coop before I would bet on anyone who farms cereal crops or livestock.
They will have it easier to adapt to subsistence farming. They should be at least familiar with basic manual farming techniques and tools. Such people are also familiar with working in groups.
The main problem for them will be, as usual during war and upheaval, personal physical security.
Probably access to potable water too as wells fell into disuse.
And obviously getting to start - initial plants and seeds.
Machinists should be able to figure things out too reasonably quickly. Reuse is big in most such situations. The more advanced hardware might be less useful or hard to maintain, but again basics are reasonably easy.
Really? I spent part of my childhood on a farm and while I could attach the mower to the PTO of the tractor and cut some hay I would not have the slightest clue how to hitch up a team of horses to do the same let alone maintain the equipment. Modern farming is about as related to subsistence farming as web development is to relay logic.
And are those machinists able to do a lot of machining without power or delivery of new stock? You are still thinking several layers of interdependence and abstraction above the long-term reality of a breakdown of civil society -- you should think less industrial revolution and more 12th century technology IMHO.
Of course, now that I write all this out I realize where I would place my bet: the Amish will rule the post-apocalyptic future...
1. Yes, if pressed to, you would get it, in a better or worse way. At least you know what to do, if not how.
You would know which plants are manageable, how to schedule crops, how soil needs to be aerated, watered and fertilized.
You can figure out suitable replacements to everything if you put just a bit of mind to it. People, even simple, can pull off feats of intellect when pressed.
2. The most accessible power technologies are wind and tidal power. Plus you can use human and animal power easily enough. And it is easy enough to make big unwieldy batteries. This is at most 16th century tech with initial development in ancient times and was initially done with ancient equipment. As long as someone remembers how it is done and how electricity and motors work, it would get done.
The hardest part is metallurgy and more advanced chemistry. That took centuries to figure out very well, though a lot can be done with wood or reed.
You can do a lot without semiconductors or with very junk big ones scavenged from about anything. Scavenging plastics is easy too.
3. The biggest risk would again be personal security and mental health. These risks cannot be avoided but can be mitigated.
Medicine would be set back by centuries. Advanced food preservation techniques would be unavailable...
Leisure would be very limited at least initially.
