He can get a non molestation order from court. It's free. They will order her to stop contact. If she claims all the calls are about the kid then he simply insists only in an emergency, anything else can be communicated via letter, email or text since she cannot call appropriately.
I would report her to the police too. After three years this is just pathetic behaviour from a grown ass woman.
The guy I'm seeing has a nut job for an ex too. She was the one who forced me into a situation where I'd meet him. Then when I called her out on some of the behaviour I witnessed, and began helping him stop her abuse, She stalked me, threatened me and my children, spread vicious rumours that I take drugs and beat my kids, threatened to track down my daughters dad who was emotionally abusive and is the reason for my eating disorder, she was gonna tell him I take drugs in front of the kids. Whenever we went out, she would text him to say she knew where we were, what I was wearing etc. I rang her social worker every single time, demanded they go to her house to check the kids weren't suffering from her unstable behaviour (it was day in day out all day long) reported her to the police. It broke her eventually and she gave in.
She still makes up rumours and just walks in his house when he has his kids. She demands to know who's the white hair are in his hair brush. She even went in his bedroom taking pics of hairs on his pillow.
The comments about appearance are bitterness. I am anorexic and she would make comments that I looked like a heroin addict to people knowing they'd screenshot it to me. It did effect me. But I'm healthier now, largely thanks to him, i dont starve myself for more than a day (I was going a full week at my worst on just water I was incredibly ill when she did all this).
The main thing is though, there's no point getting upset. I did at first. But you know what. Even if I smoked weed all day long, in front of my kids, id still be a better parent than her. The comments about my appearance are just laughable. She's morbidly obese, her legs look like a bag of onions and I'm not normally one to comment on appearance either, but I also treat people how they treat me. And my words cut deeper.
We are only a few months in. Honestly, her behaviour can be stamped out in just a few short weeks but you both need to take the proper action and keep taking it. We got brushed of by so many because he is a big guy, and there is still massive stigma and disbelief against domestic violence and abuse against men. But that's exactly what this is. It's abuse and you have to make people take it seriously.