Judging from what you have replaced/tested to resolve this I suspect something else is wrong... maybe check your fuses and also replace the coolant/water temp sensor (one on the block behind the alturnator)
If you switch on the heat it should cool down the water temp in the system to a certain degree... because ->
If you look at the coolant system you will see that the heat you getting in cabin comes from air that gets blown over a small radiator behind your dash. (thats why there isnt any heat when the car is cold) Switch that on and it brings down the temps!
This leads me to believe that something else could be wrong.