Hi and welcome to the forum.
1) Plug in your OBD2 reader again and have a look at live data for the coolant.
With a cold engine it should read ambient, as the car warms up it should reach around 70' before the dash gauge starts to move and then reach around 88' when the dash gauge reaches just under half way, if not the sensor is goosed and the car will be incorrectly fuelling.
Unplug the sensor and the rad fan at the front of the car should start working.
Replace the sensor, you car should have a blue sensor for the dash gauge and a black one for the ECU. Replace the black one with another black one, do not try a blue one as the wiring is different and do not use a brown one as they are for earlier cars and will give a false reading.
2) Do a throttle position sensor reset.
Switch on the ignition to position 2 (ignition on) but do not start the car, firmly and fully depress the car to the floor five times in 30 seconds (do not stab it).
Wait 30seconds.
Start the car.
3) Run some injector cleaner through the car and a tank full of premium (98 or 99 ron unleaded) through the car.
4) Report back and let us know how you get on.
James
Home to black Alfa Romeo 159 3.2 V6 Q4 ,green MGF VVC and red MG Maestro T16.
MG - the friendly marque.