So what are the rules of thumb for how i interact with diagnosed BPD ex wife?

[Mr. Magnet]

I don't want to make any mistakes but obviously with a 4 year old in the picture you cannot go NC

any advice is welcomed

[goateeki]

I'm contending with the exact same issue now.  Same facts, too, maybe.  Diagnosed, with a sordid family and personal history. 

My biggest problem is that the themes that finally made me pull the plug on the marriage still exist.  If I decrease contact, the angry response is "we need to communicate and be good parents to the children."  If I interact with her, then every bit of information I impart becomes something that she cites as another wrong thing I've done.  The issue between us then turns away from parenting and to anger.

Something I've noticed: there is no way to diffuse a situation with humor and lightheartedness.  It only gets her angrier. This is s useful tool in communication with every other human I know, but not with her.  It's utterly antagonistic.

She has always been an angry, bitter person.  She gets angrier and more bitter every day, it seems.

[Thunderstruck]

A very detailed parenting plan.

Most of us cannot co-parent, so we resort to parallel parenting.

Any communication should be short, factual emails only regarding the child.

[david]

I only communicate through email. Over time I have learned to minimize that too. I parallel parent and only reply to emails that I absolutely have to reply to. Even ones that pertain to our boys I do not reply to unless I honestly believe need a reply. When ex sends a nasty email and rages I usually don't reply. The only exception is if I have to send a reply about a pick up time.

Recently ex went off on S17. She called and said she was going to call the police and have him taken away unless I came to pick him up. That was the first time in three years that I heard her voice. I answered my phone because I thought one of our boys was calling. Ex called from her house phone which she never called from before. After she raged at me I simply asked to talk to S17. He sounded calm and collected so I told him that if things got out of control ? that he needs to go to a neighbor and call me.

She did this 5 years ago and I came to pick him up. I was then arrested and put in jail for two weeks because of a false allegation. If I did think I had to pick him up I would have called the police before I drove on her street and waited for them to show. Since police calls are recorded I would have made sure that I told them that I was falsely accused the last time this happened and I would be doing everything I could think of to protect myself from any new false allegations which includes recording the entire time I was in the vicinity.

[iluminati]

I echo the sentiments expressed.  Just keep it to short, direct, factual communication.  Also, avoid long term planning unless absolutely necessary, and even then, keep the details to an absolute minimum.

For example, last year, I took my D6 out of the country to visit my family's ancestral homeland.  For a passport, I needed her signature on a form.  I simply gave her the form, told her the instructions and went from there.  I then told her the days I was leaving the country.  Problem solved, the end. No discussion of her feelings or worries.  Just do what absolutely needs to be done.

[ForeverDad]

Keep in mind that trying to reason with the Ex or explaining yourself doesn't work, it is perceived as gibberish or excuses.  What you say will make sense to a normal person but it generates negative interactions with someone who's not listening or whose perceptions are distorted, skewed and biased to the person's own ideas.

So as the others recommended, state your facts or decisions as simply as possible without emotional content and hold to firm boundaries.  The back and forth of explaining yourself should be avoided, it gets you nowhere in most cases.  Yes, sometimes you may decide to make exceptions — life does happen — but be aware that these exceptions are too often perceived as the new boundaries and/or weakness that invites more boundary pushing.  You have to be the solid wall countering the relentless irresistible force.

It usually isn't as bad once you get some physical and emotional distance, set good boundaries and some time passes.  By the way, the boundaries are primarily yours, for you, there's little you can do about the other person.