AITAH for distancing myself from my stepson

AITAH for setting up boundaries for my relationship with ith my Stepson who is 15? Background: I came into SS15 life when he was 8. His bio mom is bipolar and would swing between sleeping for weeks on end to being hyper focused on his behavior. She refused to ever take meds. Dad is a very involved dad but also a disabled veteran. He has a TBI so there wasn’t much consistency or structure. I arrived and tried to build a relationship with his sister who was 12 and him. Most of the time we did really well but bio mom would occasionally talk trash and say Dad or I were stupid and lazy. She’d say I was uneducated. I have a degree in Child Development and work with children with special needs. I began to recognize from the beginning that both kids were undiagnosed neurodivergent. I have always been a gentle parent and tried to approach situations with love and logic. However this was usually thrown back in my face. Stepdaughter actually told her dad in therapy that she liked it better before I arrived because she could walk all over him and get anything she wanted. Stepson was diagnosed with ODD and provisional bipolar 2 years ago and always has peak melt downs around November (it’s cyclical). We have been working overtime to help him with this and try to make life as easy as possible so he doesn’t have any extremes in his life. We accept that he will always have challenges. We don’t have much support as far as family and friends because honestly my life has become a viscious cycle of monitoring his mental health. He has been hospitalized atleast twice a year since the age of 12 for homicidal and suicidal behavior. This last week, I saw red flags popping up and tried to deescalate issues and leave him alone. When I try to be low conflict he does everything he can to interact with me. I was attempting to go down the stairs because he didn’t want to have dinner with me. He was insulting me the whole meal so I finally removed myself from the situation. He got mad that I was walking away so he ran after me and shoved past me and pushed me and punched me in the back. I grabbed him to stop him from further assaulting me and said something serious needed to be done. I wanted to call the police or crisis center. My husband didn’t see the big deal and continues to downplay his behavior. Since then he has been more physically agressive and has called me many insulting slurs. We are talking to the therapist again tomorrow. AITAH for not really wanting to burn myself out to help this kid that is so mean and horrible to me?