You don’t need a timing light to time it. Check the owner’s manual for the procedure. You can use a 6v test light to tell when the points open.
It’s better for the engine to have a thermostat. If the thermostat is opening correctly, it should not cause overheating. You can test it as Peter mentioned above. If you are seeing good water flow looking through the fill neck the thermostat is most likely opening.
Does the car overheat at anything other than idle?
I need to see a picture of you riding around o a tractor………