Sounds like one of two things, the thermistor is reading the wrong temperature, or you have a clogged nozzle. In my experience, you shouldn't have to use a huge amount of force to push ABS through a .4 mm nozzle at 210c. These are the conditions I have and I can push filament through when the tensioning screws are off.

How is your thermistor attached to hot end? I had shotty contact with mine for a while, which caused my extruded to stop extruding mid-print (because the measured temperature dropped below minimum)