McKall, try not to grab onto that - the professional help thing. That isn't the big picture here.
He could get all the professional help in the world and stay abstinent, or he could have a miraculous healing take place and quit tomorrow with no professional help.
Or he could do everything that recovery has to offer, therapy, rehab, meetings, etc. and still go back to the drug.
The point is that no one can answer the question you are asking. If you choose to stay with him, you will always have to be on your guard. Always. Forever. The longer you spend with him, the more intertwined your lives will be and the harder it will be on you.
Your choice is to stay or to go. I agree, read all you can about this. There are no easy answers. We all are pulling for you.