Hi choca75,
Welcome to the BPD Family
I'm sorry to hear you are struggling so much with your relationship with your mom. You are not alone that's for sure, we who have a BPD person in our lives "get it".
I'm on this site because of my SO's (significant other's) uBPDxw (undiagnosed BPD ex-wife) and I would describe her as a Queen/Hermit as well... ."it's my way or the highway" and then "poor poor pitiful me".
I don't know if I have the answer to your question because each individual and each situation is different. But I did want to say that whatever you decide it doesn't have to be forever, you are allowed to change your mind, and change the level of contact... .it doesn't have to be all or nothing forever.
My SO's daughters (D16 & D20) are low contact with their mother these days. For them it took their mother doing something horrendous to each of them in 2015 that made them vote with their feet and move in with their dad full-time... .setting a physical boundary.
D20 went across the country to college her mother promising that a "family trust" would pay for her tuition and D20 who really wanted to go believed her mother despite her father's objections. She went to school for a semester and was asked not to return due to lack of payment and she is now in debt to that school to the tune of $15,000. She will not speak to her mother, blocked her on facebook, changed her phone number, very occasionally communicates via email, and has seen her maybe 3 times in the last 2 years and it never seems to go well when she does.
D20 with reason is very angry and does not trust her mother for her almost no contact is what she has to do for herself (but I also think there is an aspect of punishment here too... .that maybe isn't that healthy). D20 does not see a therapist we wish she would to work through some of this but she has chosen not to do so.
UBPDmom sent D16 went to a summer camp in Wisconsin 2014 (we weren't sure how she came up with the $5,000 to pay for it). D16 loved it, made new friends, and had a wonderful time. Mom promised to send her the next year. Again we wondered how she was paying for this... .but she put D16 (14 at the time) on the plane to Wisconsin and to camp, or so we thought. Several days later we get a call from her and she isn't at camp she is at the house of one of uBPDmom's family friends and isn't at camp at all. One way plane ticket, staying with someone she doesn't know, camp not paid for and no way home! With the help of her grandfather and uncle we got her back home. Not only was camp in 2015 not paid for but neither had camp in 2014! D16 suffers from PTSD... .needless to say this trip was very stressful and disappointing for her.
D16 has more contact with her mom via phone calls, texts and occasional trips for lunch or coffee. Even though her mother has disappointed her D16 still wants some relationship with her... .she is her mom, even if she isn't the ideal mom. D16 is in therapy which I think helps her work through things,helped her to be better able to set boundaries and has helped her be able cope with the low contact she has with her mom.
So you see different people, different situations, and different choices even between 2 sisters with the same uBPDmom.
Going back to therapy both to manage your anxiety and work through the level of contact you want or don't want with your mom might be a good idea... .it certainly couldn't hurt.
Can you give an example of how you have practiced limited contact? How close do you live to her? How is her behavior towards your son?
I spent this morning crying to my husband and later my best friend about the guilt I felt just hanging up on my mother last night to avoid her rage, anger and pronouncements that she prays to god that he will just let her die because she is sick of dealing with the people around her.
That darn guilt! I see it with my SO's daughter's too. People with BPD seem to be masters at emotional blackmail... .we call it FOG (Fear, Obligation, Guilt)
Hanging up on verbal abuse is completely appropriate but I know that's a hard thing to do when it's your mom.
Here is a link to more information on FOG... .
https://bpdfamily.com/content/emotional-blackmail-fear-obligation-and-guilt-fogI'm glad you've found us and decided to jump in an post. This is a great place for support, ideas, tools, and sometimes just a place to vent.

Take Care,
Panda39