In order to even begin to affirmatively file suit against your ex's wife, you first need to get the protective order lifted, by having a hearing and demonstrating that the allegations in it are false.  This is a complicated matter, that requires the skill of a seasoned attorney who knows (1) the appropriate motions to file, (2) how to present evidence in court, and (3) how to effectively cross examine a witness.  I suggest that you consult with a local attorney to discuss this matter in greater detail and evaluate any and all options that are available to you to remedy this situation.  Your failure to correct this situation at this point in time may result in your problems escalating as she continues to repeat these false allegations in the future.  Good luck.