I need advice for my (23F) relationship with my boyfriend who hangs onto his mother? (23M)

I’m in a really difficult situation and I need some outside perspective.

My boyfriend recently spent about 2 months in a clinic for family + other problems. During that time, there has been a lot of tension between me and his family, especially his mother. She has said that he should choose between his family or me, and I have experienced a lot of hostility, accusations, and situations that felt threatening or emotionally unsafe from their side over time. In this time I have never once tried to contact his mother, but I kept getting messages from her, but I just eventually started to ignore them. They were very threatening. For example she said that she would show up at my door.

For context, this has not been a one-time situation. For years, I have felt disrespected and verbally mistreated by his family, and I have often just tolerated it to keep the peace, even though it has taken a toll on my mental health.

While he was in the clinic, my boyfriend and I discussed our future and agreed that when he got out, he would likely come live with me so we could build stability together.

However, now that he has been discharged, he has decided that he wants to move back in with his mother for now to talk things through and try to repair that relationship. But I just know his mother will never tolerate me. She lets none of her children move out or have a relationship.

Because of everything that has happened, I have reached a point where I no longer feel emotionally safe or able to continue being in a relationship if he moves back in with his mother. It feels like a personal boundary I can’t cross anymore for the sake of my mental health.

I care about him deeply, but I also feel very overwhelmed and confused. I’m not sure if my boundary is reasonable or if I’m reacting too strongly due to the emotional situation. I'm very sad about the situation and I really love him, but I just know that if he will move back in with his mother I will be abused again by her and his father.

Any advice or perspective would really help.