Marriage ended

My husband of almost 15 years decided after an interaction we had how I didn’t feel emotional connection or acknowledgement from him lately. He got defensive that I approached him with these feelings which led to an argument of he has been unhappy for the last 5 years and worries about his mental health and would like a separation. I tried to tell him I didn’t want the separation and I felt our relationship and our daughter was worth doing everything possible to turn this around. He has continued with wanting the separation with his plan to lead to a divorce and moves out on October 1st. I struggle because the two reasons he gave I can not control or “fix” I have for the last 2 months been working on myself - quit drinking, managing my emotions reflecting and working on the things that I did that contributed to his feelings in hopes to save it. However I feel in his mind because he has so much support in his life that have gone the divorce route that this he sees as a better option. He is keeping “peace” while we live under the same roof but coming and going as he pleases without being honest with me or my daughter what/where he is going. Part of me thinks things will be better for me when he moves out because maybe I will start to feel relief. But the other part feels I have lost him for good when that day comes. I just feel sad because if he was so unhappy in our marriage and worried about his mental health he would reach out for help. I can make him be happy. I can’t make him want to seek help. But I thought I would have been worth the effort. I feel like I am causing myself more damage emotionally to be hopeful of a reconnection and recommitment after time apart when he makes it clear he wants this separation and divorce. I have to give it to him because I can’t change the way he feels.