Just to be clear. A stutter and stammer are the exact same things. Secondly I'm just getting the vibe that there's some panic here. That you think he missed out on a job opportunity because of it. Having that impression and vibe puts extra shame and stress towards your son. Which will add to his stutter. I believe you should be immensely proud of him for just putting himself out there and pushing himself in that regard. I know you probably are and you're just looking for help here but I'd like I left something out if I didnt say that. For help wise, if right now you cannot afford private coaching or therapy for your son I would recommend this book over all of them: "stuttering as a mind-body disorder" by Peter Louw. Btw what did you think a stammer was? And what did you think a stutter was?