This isn't like the homesteading days. Most of the poor still buy food from grocery stores (with cash or ebt) like anyone else.
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.
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...
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.