Wow! This is. Remarkably congruent. Thank you for being willing to discuss it!

I definitely do the worrying about people dying thing -- if anyone is late or unaccounted-for for any period of time I would always become -- I am not sure if "worried" is the right word, but I would at least obsessively consider the possibility that they are dead. This has never actually come true, but I do it anyway, against all logical argument (which I have running on a different track in my mind, all the logical reasons that person is late; it doesn't make a difference). And this happens every time, pretty much.

I get weird intense periods of mortality awareness for myself, too. The first time that I remember was actually when I was ~7 years old -- I read in some education kids' magazine about the dinosaurs going extinct and went holy shit I am going to die someday too. It is actually kind of hilarious in hindsight because I got extremely and loudly upset, but all I could articulate of this somewhat formless horror was "MOM, THE DINOSAURS DIED", and I don't think my parents had any idea why that merited mortal (heh) terror and outrage.

Less hilariously though, I definitely get similar feelings all the way into adulthood. Just uh, very very quietly, now. Thanks for bringing this to my attention; I think it will help get my various issues sorted =)