Potential Wisconsin Adoption Dissolution

We have a seven year old boy that we have had since July, 2014. We adopted him and his sister in June, 2015. Since adoption Ws behaviors have worsened 180 degrees. He intentionally is urinating on carpet in his room; in the bathroom he sprays his urine on the walls and vanity. He's very hurtful towards his sister with aggression. She's fearful of him. We can not leave them together in a room alone they must have total supervision. He's disrespectful to us and his teachers at school. He suffers from ODD, ADHD and PTSD. We have him in the best trauma therapist. He even had an inpatient stay for stabilization in a treatment hospital. MyHusband and I briefly talked about possibly doing an adoption resolution; as he is destroying our family. Am IWrong?? Has anyone done this? Any input or advice would be so appreciated Feeling SO emotional.