Unfortunately, my friend, this is where you set VERY hard boundaries, especially if your husband is narcissistic. Tell him that you refuse to be treated the way he does. If he refuses to compromise, listen to you, or continues his set of behaviors, regardless of what 'conversation' you are in, turn around and walk away, abruptly. Anywhere, really - just away. The bathroom, outside, interrupt the conversation by saying you'll be to the store and back and distance yourself from your husband doing these things. Just put your hand up, say that you just remembered you need to pick something up, and that you can both resume this conversation at a different point in time. Putting your foot down and not even letting him sidle across the line in the sand, not even a LITTLE bit, might teach him and let him know that if he continues to act or say something the way he does, then you will not listen. You won't even give him an emotional or angry reaction - you'll just vanish, therefore not giving him any attention or reaction he might want.
Also, I find it very, very strange that your therapist would say to him, "This is how you handle a situation with her." Mainly because, one, a therapist revealing personal information or coping methods for how to help you without your personal consent is a violation of privacy laws, and two, the fact that he's narcissistic already makes my eyes narrow and sends me red flags that he may be lying to you for the sole reason of 'wanting to be right' in an argument.
Please be careful, friend. The fact that you have kids also has me worried. I hope he is not verbally hurting the children either. Unfortunately that can happen.