Your responsibility to your son outweighs any duty of care to your wife.
She may have the ability to escalate and become violent to the point of significant danger to you or your child.
Everyone's definition of berserk is different so the risk assessment here is up to you.
If you have money available, remove yourself and your son from the environment.
Get a lawyer involved and ask for a barring order if possible. Once a judge has signed off on that, the police are bound to execute that order if required.
By all means if you think the relationship is worth saving, do it later on down the road, but as @bignok says, go with your gut on that one.
I for one am sorry that you and your son have to go through this. It's an awful situation to be in.
Good luck to you.