Can a recovering alcoholic use marijuana safely in moderation?

My brother is a recovering alcoholic and has been sober for over 5 years. He has insomnia and suffers from chronic back pain, many pain meds and sleeping medications are not an option for him because they work off of many of the same receptors that alcohol does. (while marijuana does not and has a much lower abuse potential) I was wondering if anyone has a personal or expert advice in regards to recovering alcoholics using marijuana to treat such issues. Just to be clear this is severe chronic back pain, including degenerative disk disease in conjunction with two severely herniated disks between the L5, S1 and L4, L5. I understand many may not agree with the marijuana as an option, if that is the case please suggest other options. As of now his pain specialist wishes to put him on opioid pain medication which I feel is a far worse option.