Sounds like ruining your marriage might be a priority on her list. How old is she?

I would really let her know that if she ever lays a hand on your son, she's gonna regret it. And I would have taken the phone out of her hands and told her to NEVER speak to you like that. If your husband isn't going to protect all of you, it appears you will be the one.

I have found that fathers are afraid to address problems because of the fear their child will no longer love them and leave. So, you, the stepmom has to be the one who takes care of the evil deed. What will you lose since she's already disrespecting you?

Can you sit her down, just the two of you, and ask her just what her problem is? Not in anger but just a talk.