I have no doubt that you have explored every possibility to stop it but generally speaking I don’t think that is the best path. Ignoring only goes so far, at some point you have to bring in the police and get court orders against him.I just ignore, ignore, ignore. It doesn’t phase me anymore.
I hope you won’t hesitate to do that if his actions continue. Ignoring him could ramp up his actions to get the attention from you that you are not giving him.
Be safe.