You are doing the right thing. Taking care of yourself is okay and very necessary. I know from my sister that this is difficult and sad and I would expect you feel very tender right now. But you are right it is in God's hands. Until your brother is ready for help and change all you can do is remain open enough so he knows you are there. This can be achieved with minimal exposure on your part, a text message on holidays or other occasion to say hello and I love you. I am praying for you both and hope for better days.
Sending extra hugs,