I basically could have written the OP. I was in therapy with my exT when I cut off contact with my mother a little over a year ago for similar reasons. I also spent a ton of time talking about that relationship with him. He was always very supportive. He even cited my progress in dealing with that toxic relationship as one of the high points of our therapy when we terminated.

Considering the fact that you're dealing with parental issues, it's not uncommon or weird at all that you regard the therapist as a parent figure.