What a brave man your brother is. If he is anything like my son, changes are hard to handle but he made a decision to change his life and remove himself from the religion and people who caused so much anxiety.
New carers will initially be a cause of anxiety but also the best thing for him. A complete break from JW world. The elders actually wouldn't need to tell the carers to quit. Unless his carers are waking up they would quit without being told.
He will be able to be his true self and have carers with no agenda other than to sincerely assist him to survive in a neurotypical world.
He will need you more than ever now. The one family member who will accept him as he is.