Long rests are great until you want bread on a Tuesday night and not Wednesday morning. I worked in a bakery for two years and we still mixed dough to full windowpane because a 4 hour autolyse does nothing if your flour is weak or your hydration is off. Try a wet dough at 80 percent hydration with just a rest and tell me how that turns out, you will get a puddle, not a loaf. Kneading builds strength you can feel, and some doughs need that work before they ever see a bowl in the fridge. Your roommate's grandma probably made sandwich bread with cheap flour, which is a totally different game than a high hydration sourdough.

Man, 8 to 10 degrees sounds like a stretch, trees are nice but that number seems way too big.

That drift after a drop is the worst part because it's so sneaky. A 6 degree error at 198 is huge, that puts you more like 192 which is way under where you want to be for a pull, and the outside of the loaf can still read fine while the middle stays gummy. The drop in March probably cracked the seal or knocked the calibration loose, and it just slowly walked away from you over a few weeks so you never noticed. I'd start checking any backup probe against boiling water before every big bake, not just when something seems off.