Man, some seriously "deep" questions to ponder. But of course ... we all go through these thoughts in our head, turning over all the "What If's".
Some of the questions are more straight forward, can be answered from experience: IE, trying out gear, trying different bike set ups, camping, what parts to carry, repairs et al.
Getting out and doing shorter, closer to home "shake-down" runs is a good way to find out if your Ducks are all in a row ... or not ... and not just your mechanical Ducks ... but that nagging "Duck" of Fear in your head.
Some may find this whole "moto ADV thing" is just not for them.

May not be fear either, just lack of interest. :confused1:
Others may become addicted and hit the road for a decade!
Some of the other questions posed are more difficult. Quite subjective, impossible to answer. Some are pretty scary prospects. But most times, once you get out "IN IT" and ON THE ROAD, a lot of that fear can melt away. How does that happen? Dunno ...

But it does!
As Tobi says ... you can't possibly cover everything, all the time, so try not to "over think" it all. Some things you will have to deal with as they appear in front of you. All part of the "Adventure" and all that.