My BPD wife says it's over, that she is getting legal council to get a separation agreement.
I honestly don't know what she will do. We have been sleeping apart since last Thursday. Eating apart (I get yelled at if I try to eat at the same time as my family). She could just be running an extinction burst. She just made a "farewell" post in my extended families fb group, and left the group.
TLDR; it's been 20 years. I'm tired.
What should I do?
This is from my own experience growing up in a similar situation, so take it from that perspective. What should you do? IMHO, absolutely nothing.
My BPD mother frequently threatened divorce but did not take action. If your wife says she wants a separation, and you do something to facilitate this- that is enbling her, reacting to her, and in actuality she may just be saying this to get you to react and not really want to do it. I can't know what she's actually thinking but my guess is that she is doing what she is doing- the separate bedrooms, meals without you and saying this in reaction to you taking control of the finances. (extinction burst).
If she were to do more than just say this- if she were to retain an attorney- then, you need to consult with one of your own. In the many times my BPD mother said something like this, she didn't take further action as far as I know of.
This advice is in response to what your wife said. Now, if you want a separation/divorce- you need to take action based on your decision, rather than as a reaction to what your wife says, unless she acts on it.
As to meals. I don't know if your wife cooks or not, but it's your family too. If she's cooking, then you can't really expect to sit down with the family to eat if she doesn't want you too, as she's in charge of the meals. However, you can eat with your children. In my own childhood, Dad took us kids out to eat a lot. BPD mother stayed home. I don't know how or why that happened. What is going on at our house then is similar in ways to what is going on in yours. If your wife doesn't want to eat with you, let her- and you go out with the kids (it was not fancy dining- we went to local diners, family style places). You are still your kids' father and are allowed to have your time with them. You don't have to let her exclude you from that.
I think it's good that you took control of the finances. My BPD mother's spending created financial stresses and issues as well. One issue is- how to handle the consequences and the escalations as well as if you want to be dealing with this over the long run. That is up to you. However, if she's just saying this and not taking action, best to not give it more attention or power by reacting to that.