Mleigh - I see my h doing the same sort of thing. He talks the talk but he doesn't walk the walk. I suspect as Job says your h was a bit scared of facing a counselor. I think once the counselor took the basic facts, the lens might quickly focus on your h and probably justifiably so?
As for what you can do to protect your son from this, I recommend validating him a LOT! And, validate him through your h. I have started to show my h how to parent. For example, s has a good report card. So at drop off, in front of both of them you tousle son's hair and say: "we are so proud of how hard you work at school! All your effort shows!" H comes to pick up son at your house and you show h some chore son did and say in front of son: "we are so proud of how hard you worked at x. We appreciate how you help out." You kill 2 birds with one stone: you validate son and teach h how to properly parent. Just something to consider. I suspect it is projection and your h doesn't have strong parenting skills.
And, I might consider throwing a joking truth dart at h for the missed appt. in due time. Next time he projects onto s about responsibility I might smile and say: "this coming from the person who was a no-show at a scheduled appt!!" And then kind of laugh and walk out the room cheerfully. I think the trick is to make it light. They have no self wawareness and maybe he needs a little help here? It's pretty ridiciculous that he doesn't see it.
Thinking of you.
Me 41, H 47, M 15 yrs, S11, S13 BD 1: 11/4/14 we work on it; really I pretzel myself BD 2: 3/31/15 H goes down to "dorm room" 8/15: H back to MBR 10/15: H back in dorm room 1/18: H files, now divorced