The point is that the right person is not at all likely to “come along.” The husband, having said that he is interested in talking to the right person, would do well to seek out the right person–right as judged by those who have bound him to discretion in the first place–by contacting the US Department of Veteran’s Affairs. They can find him someone who has all the security clearance they think necessary and who has been trained specifically to address the concerns of veterans like himself, relieving him of the responsibility to find someone they believe is suitable.
This may not be a security issue at all, nor a sin; just the horror of war.
Take, for example, being faced with a young teenage opponent who is firing at you with the intention of killing you.
Two possible scenarios:
You kill the kid. that is a horrible burden to bear; but is not a sin, and not an issue of secrecy. It is possible, however, that the whole mission was classified, which simply adds to the burden.
Second scenario: same kid firing at you; but you hesitate because he is a kid. Your buddy next to you is killed because you did not kill the kid. That too, is a horrible burden to bear.
Or you are out with your squad, and you are the only one not killed or wounded. Again, a horrible burden to bear. The mind does funny things with feelings of guilt.
Can your wife help? No - you don’t talk with her because she would never “get it”. Or your neighbor. Or your priest (it is not a sin, so why would you talk with him about it? He never served in combat. Well, with the exception of our new assistant bishop, who was running ambushes in South Africa before entering the seminary).
We are all speculating as to what is at issue, and it appears the OP’s husband is not willing to share with her. For that matter, my dad was in “close quarters combat” in the South Sea Islands during WW2 and he would not talk with anyone about it. He just stuffed it down. Most of the combat veterans I know from Viet Nam still don’t want to talk about it either. The short of it is that he does not want to talk with his wife about it, and he really does not want her suggesting others to talk with. If he needs to talk, he should contact the VA; but he has to be willing to talk.