The nature of the claims and distortions seem to me to have arrived at defamation, and you can contact an attorney in your locale to pursue that. Also, ask you attorney if there appears to have been a violation of criminal law. If so, you can report the matter to the police. DO NOT engage in any online or telephone communication with the stalker. Just see an attorney, and follow carefully the steps as you are advised by your attorney.
We do not have a client/attorney relationship until you make an appointment, we discuss your case face to face, I accept a retainer, and we explictly agree to enter into representation.
I would only add that you make sure you are keeping all of this evidence, recorded messages, printing website pages, etc. so you can show your attorney and they will give you proper advice. Most attorneys offer a free consult, so get on the phone immediately and get a free consult. Waiting is your enemy if these threats rise to the level of criminal.
The recommendations in this answer are not considered legal advice for the purposes of ethical, legal and practical evaluation, nor does this recommendation create a retention of counsel agreement between us, wherein an attorney-client relationship exists. These recommendations should never be relied upon without first consulting an attorney in your jurisdiction. I am not your attorney, unless we enter into a written agreement fulfilling the terms of that agreement. The comments posted herein are purely for educational purposes and public discourse only.