Right on!! I'll call around and see what my usual guy thinks. Gives me a sliver of hope to know some options about my next steps

Is your check engine light on?
Did you scan for codes?

I've just got a service engine soon light, no check engine light.

I can scan again, but I'm a novice at using it and am unsure what codes even mean.

Time to replace the thermostat and water pump.
https://www.youtube.com/watch?v=e1awavPWmjY

This is super weird! I actually just replaced my thermostat and water pump less than a year ago. How should I check to see if they're bad ?

I just got the car up on jack stands, and just had a realization, my car went into limp mode a while back and I took out the servo motor gear and rotated it 180 degrees and re installed it. I have a feeling this temporary solution I had a while back might be failing again now.

Take the belt off and turn it by hand. If the water pump bearings are bad, you'll feel and hear it. What brand did you use?

Get a carbon fiber gear. It will last longer. Use plenty of grease too.

Plus get a basic BMW scanner. A good starting one is a Creator C310 ODBII Diagnostic scanner. I keep one in the door tray. For more advance use, I have Foxwell.

I just got the car up on jack stands, and I popped the hood and on the damn fan clutch nut there is some wire or debris wrapped around it. I really hope the drive I took after this issue didn't destroy my whole car, I was being quite naïve assuming that it had to be a transmission issue. Hindsight 2020.

I believe I purchased the brand HEPU for the water pump

I've got a foxwell elite NT510, but I've not gotten to learn it at all.

New discovery, broken belt. Shredded in half longways, still on the pulley somehow.