Well... honestly you both need separate Therapists and couples counseling.

If you do indeed have Borderline it will be an enormous amount of work to rein it in and learn how to control your anger, and reactions ... it’s doable but it’s not easy. Have you had anger problems with past partners or just with him?

Personally I have a “ you touch me in anger the relationship is over” rule.

I can understand him just shutting down no one wants to communicate when they are being yelled at.

I am not saying you are to blame for all this relationship trouble, takes 2 to tango of course.

It’s probably good that he left, you both need time to cool off and actually look at the relationship from all angles.

Sometimes things just aren’t meant to be. You both were arguing the first month of living together?!!! not a good sign.

I hope your both able to have a discussion that is productive and not roll into yelling and shutting down

Good luck