Those are all good observations. Acting like it doesn't exist at all isn't good either because it's clearly distressing the child, they don't know what's going on, and everyone is acting like nothing is happening which is also very confusing. Stuttering is still stigmatized in society so ignoring it won't ignore the stigma they are feeling. If they are struggling a lot or worse, talking less and being more quiet than usual, that is a clear sign that they've already picked up that stuttering is bad they shouldn't do it. And ignoring it won't help with that. But it sounds like he has verbalized his frustration and you have acknowledged it's existence and frustration but don't know how to talk about it which is totally expected since most people don't know anything about stuttering (even most SLPs unfortunately, or they know outdated harmful information). I would look for a good speech therapist recommendation. I would be mindful of the faces you or your husband make when he struggles and encourage him that you want I hear everything he has to say and show patience. Unhelpful stuttering behaviors get reinforcing out of a desperation to do whatever you can to stop stuttering, but in the end they just add more crap on top of the speech pattern. A good SLP can help stop or replace those behaviors with ones that allow for more natural stuttering which is not inherently tense or struggled. Tell him that stuttering is ok and that you care about what he has to say, not how he says it.