Dark Souls?
Pretty much, I'm looking for a game where I'm not the hero, I'm not the protagonist, I'm just a pawn in the big picture.
You're just one of the many undead who try but eventually fail. One of the first characters you meet makes sure you know this. :)
Preferably a game with a big open world too, one that feels real and isn't just a predetermined path for my player.
DS1 isn't very large, but there's no predetermined path at all, especially if you get the master key. DS2 isn't as open, but you still have multiple choice of routes. DS3 is limited in this regard, though.
I also like games where you aren't clearly stronger than all your opponents like you're some sort of God so they actually feel intimidating and there is a fear of dying
That's the hallmark of the Soulsbourne series as a whole.
I found out this helpful guide on r/flexibility. I've only tried the starting to stretch program using the follow along video a few times, but I didn't do it long enough to notice improvements. It was pretty convenient to do it, though, since you can do it in your own room, and it's only 30 minutes thrice a week (or 15 minutes 6 times a week). Maybe it'll help you.