On a turbofan engine, the best measure and control of thrust is by fan speed (N1). This is because all of the air is pumped by the fan rotor, whereas the core rotor only handles a portion of the airflow. EPR or core speed is affected by various parameters and is not an optimum manipulated variable to set fan speed.
This doesn't work very well after bird strike damage or inlet damage. Lots of speed not so much flow.
My recommendation is to monitor aircraft speed vs pitch as well.