Sending strength, hummingbird. He is exactly where he should be, surrounded by the very people who are trained to help him.
Is his counselor part of the treatment center? If she isn't, I would take Seren's suggestion and let the staff at the treatment center know what he is telling you. The counselor may not be writing you back because her relationship is with your son and she may have boundaries around discussing her patients with anyone. I am so sorry both you and he are going through this.