Stop trying to "help", because obviously it won't make things better for you guys. Just support him and accept his stutter the way it is now. Yes he might be more fluent after doing exercises but this is not a permanent solution. The thing is that he obviously knows what works long-term and what doesn't. People who stutter are usually very very sensitive about it. We don't want people to tell us to talk more slowly, to do breathing exercises and so on. We know you mean well, but most of us knows that those things you suggest won't help. Trust me, we have tried everything possible, because let's be real, who wants to stutter? Please just be quiet about the subject and let him talk about it when he he is ready. He might never want to open up about his stutter, but just keep supporting. :)