Sadly, I dont have the answers for you but what I do know is theres only so much you can do. He needs to decide for himself he needs help, its up to him to take responsibility and go back to the GP. It sounds to me like he should be having a review and either increase his dose or change treatment. However, as a sufferer of anxiety/depression myself it can sometimes feel like being trapped in a living hell. I feel for you both as its not much fun for either of you. I wish you both luck and hope he finds the ability to reach out for professional help sooner rather than later.