You're doing fine. My step father was a complete arsehole about it, I'd string a few words together at speech therapy (as a six or seven year old) then go home stutter most words and get berated, as though there was anything I could do about it and I feel this made it worse. It was already a poor environment to grow up in and school made it worse still. Going of what you say, your boy is already in the perfect atmosphere to hopefully keep his stutter under control. School will be a different issue. It's there that you'll need to work with teachers to ensure he's not teased about it.