I had a few similar issues, here is what I learned:
1.
Kreek wrote:If you hit CTRL+D (I'm not sure if it works on the default client) you get a light meter window. There is a value (either d or b) that is equal to 62.75 when you are not in darkness. As this value decreases, the deeper into the darkness you are.
2. Yes. In fact, I ended up setting up in the darkness without even realizing I was in it (Before I learned about the tip from Kreek.) I thought because I wasn't losing humors, I was no longer in. A week or so later, my humors were all around 20 higher, and areas where I was losing humor before, I was no longer losing humor in, so it looks like the more humor you have, the deeper you can go before you start losing.
3. I saw more signs of life near or in the darkness than I did for around five hours worth of travel before getting to the darkness, so my guess is "yes".
4. No. I live in the darkness and always log off and on at my settlement.
Regards,
Ez