The oven temperature can NOT be calibrated/adjusted on your specific model range. If it's cooking 50 degrees to cold, set the temperature 50 degrees hotter when setting the bake temperature.
I do not know what type of oven thermometer you are using but most of them are slow in reacting and showing the actual oven temperature. Set the oven for 350 degrees and let it cycle for a minimum of 5 cycles before comparing the temperatures. The oven temperature sensor can cause incorrect operating temperatures if it does not have the correct amount of resistance based on temperature. The oven temperature sensor probe should measure 1091 ohm of resistance plus or minus 5.3 ohms at room temperature of 75 degrees plus or minus 2.5 degrees.