Is a 4 Ohm reading on a dryer heating element bad?
Was your breaker tripping? Did you disconnect the element before taking your resistance reading? If you put 4 ohms on 240 volts you get 60 amps. So I suspect your heating element has some inductive quality you are not measuring with your meter or it was still connected in the circuit. Otherwise, your 30 amp dryer breaker would be tripping. 

Resistive elements don't normally drop in resistance. They usually open up. This would mean you would get a reading of infinity (open) with your meter if the element is broke. I would more suspect something in the controls, like your low temperature thermostat is not closing to turn the element on. (is that what you called the Thermal cutoff?) Or the contacts on it are burned beyond usefulness.

Sounds like you are getting good experience at troubleshooting electrical here.