More evidence that he has, the better.
I would suggest that you kept a detailed diary even when things are going good or bad containing anything that may be slightly untoward and he makes a note of dates and times. Make sure she doesn’t see it!
Discuss things with his solicitor and express his concerns.
I would suggest that he tells the police exactly what he is going to do to leave her and expressed his concerns to them that after she goes, she was going to make unfounded allegations because she has been blackmailing him (making unwarranted demands with menaces) that if he leaves, she will do this that and the other.
If he has Text’s what she has threatened, he should make sure that he keeps them. He should keep dated photographs of his scratches.
if any previous incidents have been reported to the police by her and nothing has happened with them, he needs to make sure he has those dates and times and puts them in front of the police when he sees them.
If he is genuinely concerned about this, he can literally walk out and then apply to court for an emergency injunction to stop her contacting him. That would only be pending a full hearing and it’s a 50-50 chance he would get the injunction. Ultimately, what he is trying to do is protect himself from her lies.
Generally, the police will favour whoever makes the first report.
A you appreciate, there is no easy solution to protect your son from the lies of an accomplished and convincing liar.
If he can secretly video her tantrums, although they may or may not be admissible in court, they would certainly help to stave off any police action.
Can I clarify anything for you?
Please rate the service positive. It’s an important part of the process by which experts get paid.
We can still exchange emails.