Misconceptions regarding stalling
An aircraft only stalls when the wings critical angle of attack is exceeded. This has nothing to do with TAS. If you fly an aircraft that is overgross weight then the angle of attach must be increased to produce enough lift to get that extra weight off the ground. This works up until you reach the critical angle of attack.
To climb with that extra weight the pilot had to use a slower airspeed than normal climb speed. This is what is causing the engine to overheat.
Your right about all the standard numbers you stated as being incorrect.