You may have a lawsuit but will have to prove damages. Other than this being a juvenile prank for which he should be ashamed, unless you were harmed in some financially compensatable way, or unless he made you a victim of identity theft, there is a misdeed without harm. In which case you may win a judgment but no money.
Have your lawyer send a cease and desist letter. If that fails to curb the sophomore in him, seek an order of Protection and enforce any violations of that order to the fullest extent.
I'm sorry that you are in that situation. The above response is spot on. The irony is that when I read his fake post it insults him more than you by saying that he 'can't perform anymore'. Not only is he a jerk, he can't even insult you correctly!