Have you tried having him diagnosed with ADHD or to see if he is bi-polar?
Obviously the situation has become critical and the prognosis is not good. If your grandson is to improve, he will likely require a very structured, supervised group living situation, such as a residential treatment center. It is likely that, without intensive 24-hour/day intervention, he will become involved in antisocial behavior of a criminal sort at some point. It is not too late, but time is running short.