HoCoRat - these are awesome questions.

As for your comment about "hiking maps" not showing your updates -- this will take some time. Each of the hiking maps you use that consume OSM data updates their "version" of the data at their own pace. You can expect to see these changes reflected there anywhere from 3 days to 6 months from now.

Generally speaking, though, deletion is almost never the best option. You can use tags like "access" or the "abandoned:" lifecycle prefix (abandoned:*=*) to indicate that a feature is not usable or gone. This helps folks who edit after you know not to add it back.

On the flip side -- if something is on the ground that's not on the OSM map, please add it! You can use your own GPS info, or you can trace imagery.

The rest of your questions largely pertain to "access." As you've discovered, there are quite a few nuances to this discussion.

If you haven't already, I'd encourage you to explore the OSM Wiki page for the "access" tag: access=*, and the links on that page.