Dr's use the FEC/Functional Capacity Evaluation to determine what your permenant restrictions are when writing the final report at MMI/Maximum Medical Improvement and issuing a PD rating.
What the PT/Dr administering the FCE says is not really relevant, generally these are PT/Physical Therapists who do the evaluation.
If your Dr says you cannot return to your pre injury job, you should be eligible for VR/Vocational Rehab services.
If you disagree with the Dr report...go back to your Dr, and get clarification. You may be seen by an IME/Independant Medical Evaluator.
WC is full of litigation when there are disputed medical issues. It may be in your best interests to consult with a WC attorney. You may also need to file for a hearing in WC court for a judge to determine the issues.