Benjamin S. Wolf, the legal director for the American Civil Liberties Union of Illinois who for years has made his mark representing people with mental illnesses and children in state custody, is stepping down.The organization announced this morning that Wolf, 65, will vacate the spot in the near future. He will remain as a senior attorney with the group and provide counsel on his replacement.“I think we’ve built a remarkable legal staff at the ACLU of Illinois,” Wolf said in an interview this week …