I am stuttering since I can remember and I can assure you that my mom stopping me, always mentioning stutter, reminding me I am stuttering was reason why it dragged into adulthood. Also my parents were all the time arguing with each other and yelling at me. Try to create calm, safe space for your boy. Other than that I don’t think there is much you can do. Just calm, safe environment was something I was needing in early age.