I live in the Yukon, there is no mechanic around that is volvo familiar, so trying this first in case someone can guide me to fix my problem.

Symptoms by order of appearance:

Sporadically (once every other month specially on very cold weather below -20C) I'd get a reduce performance engine sign which would go away alone in a few minutes and never affect the driving, just the message on the car's panel.

This summer I started getting more frequent Reduced P. Engine warnings but now the car would go occasionally on Limp mode. After restarting it would "fix itself". No codes, just the message with it's amber exclamation mark.

Then I got rough idling (still no CEL) and poor acceleration (it makes sense if I do have a faulty throttle pedal position sensor) But It would go away after a few hours of not driving.

Then eventually I got my first CEL and codes are:

P0638 ECM-91A7 Throttle unit Faulty signal
P0123 ECM-9150 Throttle unit, potentiometer 1 Signal too high
P2135 ECM-903C Throttle position (TP) sensor

What i've done:
I cleaned the MAF with CRC and changed the filter when I thought it would fix the rough idling.
When I finally got codes I cleaned the throttle body (to the best of my capacity), checked fuses (ok), and car runs ok but codes and symptoms come back randomly. Sometimes as soon as car reaches temperature, sometimes as soon as I accelerate over 70kph, I never know.
Is it true I need the ECM to relearn that i've "cleaned" the throttle so the codes and symptoms would go away or am I miss-interpreting? eg: disconnecting black cable off battery.

After reading a bit I guess my best move would be to get a new TP buuuuuuut, I'm still uncertain if this is the issue or I'm missing a more obvious DIY solution. I don't understand why the issue is intermittent, if a cable or connection or sensor are bad, wouldn't they always be broken?

Could I be testing the TP sensor with a multimeter? If yes, how.

I also got overwhelmed reading about "xemodex", orange label, white label Throttle body, VIDA, re-programming, not reprogramming... I feel like i wanna do all my homework but also I would appreciate so badly someone guiding me on the order of things.

My scanner is a Foxwell NT301 so I'm pretty limited.

Thank you all,