Can resistors be used to bring a heating element within range?
Could this be a thermistor instead of a thermocouple?


Could be either, thermocouples usually put out microvolts. If it's a thermocouple, you'll see the voltage vary by a small amount with temperature. 


  Also, is it possible to correct the resistance range by adding a ~50
  ohm resistor in series with the heat sensor?


It's possible to correct for one temperature point with a resistor, but if your adding a resistor to a thermistor, this will shift the entire curve up and will not be equivalent. This will most likely cause problems for the control circuitry, and the temperature display. Your best bet is to find an equivalent temperature sensor and swap it out.