Does the computer reboot after opening any program or anything that is intensive for the computer? If so, it could be a PSU problem, if you have another PSU sitting around by chance, just change the plugs, you can keep the other PSU outside of the case to see if it works

I’ll mention again, those temps aren’t to high for a laptop, you may get another year out of the paste before needing it replaced

Counting your laptop works fine, sounds like you lucked out, if it ever happens again just leave your computer off for a couple of days and the water will evaporate, unless you have a high end computer witch usually has water damage markers witch turns red with contact of fluid, there isn’t an actual way of telling fully

Counting windows works fine in safe mode, it’s not a hardware issue right out of the box, sounds like windows got corrupted, or there is a failing driver, ensure that all your drivers are installed and up to date, including your bios, if it still doesn’t work I would revert to windows 10 like you said as it is more stable and supportive

Having those temps aren’t too worrying for me for a laptop, and if it’s a older computer to. Thermal paste usually last year’s before needing replacement, and thermal pads usually last forever as long as there’s been no damage. If you still want to continue on, tech shops usually have a fixed cost to touch your computer no matter the work required, they usually have it on there website but can range from $30-$100