when people are good listeners, it usually helps me relax, which in return helps me stutter less. in my experience, having a good listener helps me feel "normal" if that makes sense. if im stumbling over words and the person im talking to maintains eye contact and acts like i didnt just get stuck on a syllable for 30 seconds, it really does help. it makes me wanna talk to them more. just know he appreciates you so much more than you think. goodluck to you and him