I'm sorry you're going through this.

When I was little we adopted a very abused dog named Pepsi from a bar where she had been hanging round. She was great with me and my mom, but was very skittish and aggressive when surprised by new people.

In the end, she attacked one of my playmates. My mom had her outside and had warned the girls father (who was doing work on our house) to keep the girl and the dog separate. The dad forgot/whatever and the girl got bitten pretty badly (Face and arms). We were liable for all of her medical bills. We would have paid anyway and our insurance covered it, but my point is: our dog had never bitten before, we gave warning, and arranged for separation, and we were still liable (morally and financially). You have prior knowledge, a history of biting, and are not adequately separating. You would be super liable (morally and financially).

My friend and I never really hung out again. I saw her at a wedding a few years ago, and the facial scarring is still somewhat visible. I also imagine it was deeply traumatic emotionally.

Pepsi was taken by animal control and put down. And actually it was kind of sweet. The animal control guys were great with her, letting us say goodbye, feeding her cookies and treats, baby talking her. I do not think she was aware of what was coming and all things considered, I think being gently put down was better than living her life so stressed out and scared.

It's not the dogs fault. It's not your fault. But being a pet owner comes with responsibilities. Your boyfriend is accepting the responsibilities of working with the dog, loving it, and caring for it. Unfortunately, he also needs to accept the responsibility of releasing the dog from her obviously astronomical levels of stress.

He needs to accept that sometimes you can't save someone, even if you love them. It's not a failure, it's just life.

Would he stay with you if you were a heroin addict and had begun stealing from friends and family for your next fix? (Hopefully) the answer is no. Because that would be enabling and would hurt everyone. The argument that he couldn't give up on you because there was a clinic in Montreal, or a new treatment, or spirit healing that he hadn't tried for you yet wouldn't hold up. He's enabling the dog in the same tragic way, but unlike an addicted human, the dog cannot help itself. He needs to accept he cannot save her, and that the best he can do is end her stress.