Tin (mostly due to glass-production) and Phosphorous (for fertilizers) are two more example of chemical elements that we are running out of rather quickly. Not completely and irreversibly, but enough to cause insane price-spikes.
Sand, including high-purity silica-sand for chip production are also running low, and aren't easy to replace.
Those scenarios seem way too underspecified for me to be able to provide an answer. The answers I would give, particularly for question 3 and 4, totally depend on what exactly the side-effects of the killing and taking of money would be. Would other people be able to find out about this? Might they become concerned that the same fate could befall them, etc. etc.
I don't know where you live, but in Europe you can get your antibody level measured for around 50€.
Saying "if you are worried, you should get your booster" is not at all equivalent to "if you have gotten your booster, you should not be worried about this virus".
The first statement permits that one can still be worried after having gotten one's booster (just a little less), which the second statement does not permit. Therefore, those two statements cannot be logically equivalent.
If you had written "if you have gotten your booster, you should not be as worried about this virus [as before]", that would have been fine.
Thank you, I had no idea markdown needed to be actively activated in the profile.
There's this post, which suggests that Original antigenic sin is unlikely to be a problem. I really hope that's true.