It seems you are at the point of no turning back with your wife. No longer are you able to pretend that the marriage is going to work out. When we just can't do it anymore with the disordered person/people in our life, we naturally start to set boundaries that are going to get a lot of pushback. It is so hard to maintain that balance of what is just going to come out because you can't do it anymore which gives your wife a heads up that something has changed in your relationship, and she will definitely act out to the changes.
When I hired a lawyer to deal with some legal issues with my sister with Narcissistic Personality Disorder (NPD), I refused to have any direct contact with her, despite her continuously sending me letters through her lawyer. You are living with your wife, so you do have direct contact with her. It might make sense to tell her the new boundaries and then walk away without staying involved in her meltdowns, letting her know she is in charge of her dysregulated emotions. Clearly there is no point in letting her know about the divorce proceedings until you have your ducks in a row, your finances organized, and are in agreement with your lawyer on how and when to proceed.
Good job in finding a lawyer who understands high conflict divorces! Your lawyer is probably going to advise you to reveal as little as possible to your wife. My lawyer did not share nearly anything with my sister's lawyer whereas her lawyer who came from a top law firm, seemed to think that intimidating me was the way to go and it did not work. I was way to aware as you are, that there is no such thing as any kind of peaceful reasonable negotiations with an extremely disordered person.


