The next time she calls, pick up the phone and say ever so sweetly, "hello, may I help you?" See if she says anything. I suspect she calls, breathes into the phone or does nothing just to bug you.
Of course, you could do like I did many years ago when I had this happen one too many times...I answered the phone "hello, city morgue, may I help you? Are you calling because you have a cadaver that requires picking up? If so, please provide the name, phone number and address of the location and I will have my team come out and pick the body up. Our motto is you stab them, we slab them. We'll be happy to put the body in the cooler until you decide what you want to do about funeral arrangements. I'm sure the coroner can be reached at this hour and w'll be happy to contact him as well." She slammed the phone down and I never got another call from her.
Doodles, you can't worry about her getting arrested...she's crossed the line. Her behavior is based on on security issues. Also, the calls are to drive a deeper wedge between you so that you will gie him what she wants...divorce. The ow sees y our h is waffling on the fence and a wuss, therefore, she's starting to take matters into her own hands. Once she feels her mission has been accomplished, she will crawl back into her hole for a while.
His odd behavior could be both he and the depression/withdrawal. You don't know what she's said to him about the situation. It could be she's threatening him and that's why he's staying away. There's no use worrying about something you can't control or repair. This is defnitely his mess and the fallout is hitting you and your son. Please protect yourself. I don't trust her.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.