@shakespeare47 I have dealt with similar type treatment from my wife. I'm sorry you are going through this. It is really hard because of how tangled everything becomes in marriage. Finances, friends, family relations, and children all are added things that weigh on a decision on if it makes sense to separate.

It sounds like you do have a therapist that you are working with.
Please bring those direct, hurtful comments she makes that are used as attacks on you to the therapist. They may be able to give you the best way to handle the situation since they know your story more deeply than we do.

I started to confront my wife when she would make the cutting remarks.
I've been sort of her stress punching bag and she says things to me she would never consider ok to say to anyone else.
She says things to me she reprimands our kid for saying to other family
members or his friends, but I am supposed to take it and just how she 'lets out stress.'

I finally said to myself that if she is going to be critical of me anyway, I'm not going to worry about her reaction in confrontation.
I don't know that you can confront her in the heat of the moment as you process the comment, but going back after you have reflected on how a comment was received and made you feel, you can simply tell her, "You were pretty cruel when you said .... The implcation of your words was ..., which is pretty hurtful and mean."
In my wife's case when she was making her cutting remarks that carried really hurtful meaning but didn't outright say something. Once confronted with the meaning that she sent across she started trying to make excuses for what was said but direct confrontation did tone down her remarks a lot.

Good luck.