Hi, I'd like to help you with your question.
It sounds like there is a lot of enabling going on in the family which is probably causing much of the boy's acting out with the counselor and refusing help. He knows that if he acts out, his parents and grandmother will back him up. There are no real consequences to his behavior.
Given the family situation and the history of drug and alcohol use, I would highly recommend that all family members seek help. They need to understand that in order to fix this problem, they all have to change their behaviors and stop enabling this child. Once he turns 18, he will be an adult and they will no longer be able to have a say in what he does. If they have the opportunity now, they should learn how to cut off the funds, treat him with discipline and get him the help he needs.
They can start by calling the local community mental health center. The counselors there can help them find help and connect them to inpatient and outpatient treatment facilities. Mental Health centers work on a sliding fee scale, so depending on their income they could pay very little or full fee. Community mental health also takes insurance so they could use that as well. Here is a link to the local center in Denver, CO.:
Here is also some books they can read to get started. One is called Facing Codependence: What It Is, Where It Comes from, How It Sabotages Our Lives by Pia Mellody, Andrea Wells Miller, and J. ***** *****. Also, Don't Let Your Kids Kill You: A Guide for Parents of Drug and Alcohol Addicted Children by Charles Rubin. You can find these on Amazon.com or your local library may have them available.
I hope this has helped you,