It is time for you now.
Because when he/ they eventually are ready for recovery you will have the strength to help them. Until then step back. That might be asking to him leave the home, don’t lend him car, shop him. Stop the money giving. It will get harder before it gets easier. It sounds like you have reached your limit. Go to the substance misuse teams speak to them yourself. They are great at helping you find the strength to move on.
Good luck