My H and I had the worst discussions about everything for that first year especially. I think many WS, especially remorseful ones, feel guilt and shame about the A and it is common to be defensive when we feel those emotions, if he was nervous about the MC and perhaps anticpating being attacked, he may have been defensive before walking int he door. I don't think that means that he is hopeless but I think it might require some careful conversational strategies on your part to get past his barriers.
A quick example would be recognizing and agreeing with his declaration "yes I know that you feel confidant you will never have an affair again and the work you have done to show me that has helped me so much but I sometimes feel insecure when you have to work late, it reminds me of how it used to be and I might need some extra phone calls on those nights"
That may not be your issue but you get the point it was specific, you validate what he said, then you express a specific issue you have in a calm way non accusing way and give him specific way to help you.
I thought that we might have to D if my H and I couldn't have a conversation w/o him getting defensive so I had to learn to do it differently. When I changed my side of the conversation my H just followed my lead, things got so much better for us b/c I was able to get to the discussions I needed. Fight the urge to get defensive back, just remember if you react as you always do, you'll get the same response you always get.
Next time he says something defensive, close your eyes, take a deep breath, remind yourself that he is reacting from fear and confusion, he doesn't know what to do or say to make this better so rephrase whatever you said to give him a clear way path to you.
On a side note, at first i thought if I have to tell him what to do it won't help me, but i was wrong! The first time he said "ok I'll do what you need" instead of "why do you always bring this up!!??" I felt so great, so happy, so loved!! And the best part was after doing specifically what I asked a few times, he kind of got the hang of what I needed and started doing stuff on his own that was perfect.
A big part of this is they don't know how to fix the mess they made and it's sad and frustrating and confusing couple that with guilt and shame and you get defensiveness and lashing out.
Help them help you.