A very difficult situation, of course, and his mom and he are so fortunate to have your support. As well, like gcv mom said, you are between a rock and a hard place.
I don't think it is necessary for you to apologize. You are doing the best you can to help in a very distressing situation. You care for him as you do your own.
What I stated in my earlier post,
"The other posters have good suggestions, and maybe medication will be the first step towards him getting on the right track. Good luck to all." : I have this thinking regarding medication as relates to my son -- that is, if we could find medication that would be effective for him, it might open doors for him; just thinking along the same lines and did not mean to instruct or criticize.
Take care.