I’m not a Buddhist, but I’m struggled a bit with some similar concerns. I think there is a lot of value in making a careful distinction between a person being responsible for what they do, and being to blame for what they do.

Consider a mistreated dog, that bites. It’s not to blame, but it is responsible in the sense that we need to take practical steps to deal with the danger.

Establishing a boundary between oneself and an abusive person is not different than putting on a coat to establish a boundary between oneself and a cold rain, it’s a practical measure, not a moral judgement. It can be done without a feeling of resentment or hate or fear, and it need not come at the exclusion of compassion and understanding.