After some very scary domestic violence incidents, I left with our 4 year old
It takes so much strength to leave, and for a lot of us the leaving was long overdue. I hope you and your son are doing ok after what you've been through, and are starting to pick up some of the pieces.
And glad you reached out. It really does help.
I feel like I will never get away from him
I read somewhere that it takes two months for every year of marriage to recover from an abusive relationship. Words like always and never tend to come up for us because these divorces tend to trigger depression, which can feel like dread. One of the worst feelings. And then it starts to get easier to create psychological and emotional distance. If you find yourself feeling "always" and "never" that's usually depression talking
He insists I am a terrible mother for any and all petty reasons
So much of what someone with BPD says and does when dysregulated is projection. If you swap out the pronouns it can give you a pretty good idea of what he thinks of himself.
I am so tired
No doubt you are. Are you getting any kind of break when your son is with dad?
he sends me pages and pages of paranoid rants about COVID-19, insisting I communicate with him for our son's "best interest." His messages are almost always peppered with insults and threats
I had all emails from my ex forwarded to a friend who would let me know if there was anything I needed to know or respond to. There never was.
How on earth are we going to co-parent?
Even in low-conflict divorces it can be best to start with parallel parenting until emotions have cooled. It's amazing how successfully you can raise a child when there is very little communication between parents.
Your ex probably expects you to do all the work and tell him everything that's going on. I guess it's time for him to learn that arrangement has ended. And if he wants cooperation he has to at least learn to control his impulses to insult and threaten you. Short of that, assuming he's going to struggle with that basic nicety, you'll probably find that parallel parenting works best.
Do you have any pressing co-parenting concerns?
Is he communicating at all through the parenting app?