Oh another thing i just in your post, your son masking the y…y… y.. or using shorter sentences. This is because he was made aware of his stutter in a way that he is now covering up that sound. My son never did or does this. We patiently let him finish the sentence. I’ve never told my son that his speech is different. He is aware because he goes to therapy and his therapist talks to him in a way where he knows he has stutter but he also owns it. He still confidently talks. My son has recently started having blocks. We patiently let him finish his sentences and don’t interrupt him.