Kinda weird temperature readings

I hate to tell you this, but your car is at the end of it's service life.
It's time to take it to the scrap yard and buy a new Toyota.
This is the only sensible solution to your problem.

Or you can follow the advice already given (which is excellent), fix it for under 20 bucks, and keep it on the road for another 51 years.
Go with option #2 keep it on the road another 51 years