I also had delayed speech. Had speech therapy in school and other various programs starting at 4-5. The biggest thing I would say is don’t tell him it’s probably going to go away. My mother was super supportive in every other way..read all the current scientific notions, drug me around to all the speech therapies, lots of pep talks...except for this one thing. Being told it was almost a certainty that I would grow out of it left me feeling pretty devastated around 12 or 13. While I understand as a parent, you want to “fix” it and reassure your child that it will get easier there is a 10%-15% it’s always going to be hard. No matter how much you’ve researched or how much speech therapy has been administered. If I was afforded the space at an earlier age to accept it, i think my overall perception of my self worth would have benefited.