I’m not a lawyer and I don’t know your state laws. That said, I’d pursue the lawyer.
CPS in your state most likely has a certain minimum number of actions that they have to take when they receive a complaint. Getting a lawyer to contact them and let them know you’re now represented may not eliminate all of the grief, but it could get them to make things much more cursory.
You might also find that you can have an injunction put in place without too much trouble or expense. If she’s on a fixed income she probably can’t afford someone to fight it. Maybe you’ll get your dream scenario and she’ll show up in court acting like a lunatic. Either way, you’ll have done something that’s important to improving your situation. You see, right now she gets a free roll at causing you grief whenever she wants. It doesn’t cost her any time, trouble or money to pick up the phone and screw with your family. Any decent lawyer is going to try to shift it to where the default situation is you being left alone.
Find someone you trust who got divorced and was happy with their lawyer. If they don’t handle this kind of law, they’ll know somebody who does. Don’t pick one off of an ad. Word of mouth only. Your first consultation will most likely be free and last an hour. At worst, it’ll cost you $100. Any more than that and you’re at the wrong place. Good luck.