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I am sorry to hear about this situation, Mark.
First of all, if he is threatening your life, you want to go to the police and file a police complaint. The police can and normally will look into the matter. He may be charged with what is known as a terroristic threat under Title 18 § 2706. See HERE.
Also, you can sue him for defamation for the accusations he has been posting about you. The burden is on the plaintiff to prove: (1) The defamatory character of the communication. (2) Its publication by the defendant. (3) Its application to the plaintiff. (4) The understanding by the recipient of its defamatory meaning. (5) The understanding by the recipient of it as intended to be applied to the plaintiff. (6) Special harm resulting to the plaintiff from its publication. (7) Abuse of a conditionally privileged occasion. 42 Pa.C.S. § 8343(a). You can get actual and punitive damages plus legal fees if the claim is proven true.
A threat to do this, or, actually doing so, may be a good way to go about having to stop him.
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