I am concerned for my wife and kids both. I also fear that my ability to trust her has been irreparably damaged due to her lack of transparency / lies.
You sound as if you are still in victim of abuse mode. At this time you are standing on the train tracks and watching the train coming at you - you will need to make a decision. Are you going to let the train (your BPDw) hit you and then apologize for throwing it off schedule or are you going to step off the tracks and give you and your sons a chance at a less chaotic life.
You did not mention whether your BPDw is undiagnosed (uBPDw) or diagnosed (dBPDW). It doesn't matter a lot as the behaviors are similar, but it does matter in how you present her behaviors to the support your case.
Keep coming back here and you will find a community ready to support you that has walked the same path you are facing. BPDs tend to follow a very familiar pattern aimed at continuing to push your buttons and keep you under control, hence your stbx trying to catch you off guard by filing first. While it is not in and of itself a huge legal advantage, it does signal that she is probably 10 steps ahead of you already. I am going to post below a list of the common advice I give to people who are beginning this process. It is a compilation of advice given on this board as well as few other forums i visit.
I promise you there is a better way than what you have been experiencing for the last 21 years.
1) Get a therapist for yourself. Not a marriage counselor, but someone whose job is to help you get your head on straight in this incredibly stressful time.
2) Get an experienced divorce/family law attorney. This is also not a job for new attorney. If you interview an attorney and he or she says they always settle and you will not need to go to court, that is not the attorney for you.
3) Be prepared for the false restraining order. This is a very common reaction from the BPD playbook.
4) Get a digital audio recorder or two. You should never be around your stbx without a recorder running.
5) Don’t be afraid to tell family and friends. Too often we try to hide what is happening in our relationship from a sense of embarrassment, pride or fear.
6) Have an emergency escape plan. This often dovetails with beginning to reach out to family and friends. In many states if there is a domestic violence complaint, one of the parties is leaving the house for the night. Even if you are innocent it could be you.
7) Videotape the house. There is a very real possibility that your stbx will lock you out/ destroy things/ sell things, etc
8) Document, document, document - If you have kids, you are likely their best connection both to reality and stability in the chaos of the BPD. Once of the best tools at your disposal costs nothing but a bit of your time. A simple journal of what you do for your kids each day. If you can add pictures and mementos, even better.
9) Don’t take legal advice from your stbx. You may find yourself at the end of a stream of threats from your stbx about what the courts are going to do when they report all your transgressions. Tune it out.
10) Don’t expect the process to be cheap or fast. Remember that pwBPD usually feel very entitled and in fact if you quiz them they often have a very distorted sense of what it really costs to live.
11) Take action to separate your finances. Redirect your pay into an account into which only you have access. Cut off joint credit cards. This does not mean stop paying the bills, it simply means you control how they are paid.
12) Avoid face to face or telephone communications whenever possible. pwBPD live for the conflict of these and you have no documentation of what was said. Email is always preferable.
13) Practice radio silence. You communicate only about what issues are essential to get through the day, such as kid’s schedules, etc. Your job is not to look out for your stbx. Preferably via email.
14) Make copies of all important documents you may need and store them in a secure off-site location.
15) Do not expect a neutral playing field when dealing with custody evaluators, guardian at litem, friend of the court, etc. Do not get drawn into bashing your stbx. The goal is to show how involved you are with your kids.
16) Don’t be in hurry, especially with a high functioning BPD. Time provides a chance for you to document your pwBPD unstable behaviors, which they might hide over a short term. The goal is not to have them diagnosed, but simply to show patterns of behavior.
Again, welcome.