Talking to your dad
Unfortunately, unless your dad is ready to talk with you, or somebody else, there isn't much you can do. Your mom's reaction to some of the things your dad might have related to her is a natural reaction. Most people by nature are appalled by the things that are done by necessity in a combat situation. It is extremely difficult to understand what it was like for your dad without having been there.
My dad was in WWII, Korea and Vietnam. To this day there are lots of things he has never discussed with me even though we followed similar career paths. Even when he used to get together with some of his flight crewmembers they would begin to talk about things and all of a sudden all of them would get real quiet when they got too close to a painful topic. Even though I have been there, my dad will not discuss certain areas of the things he did, saw or heard about.
Although I would love for him to relate some of his stories, I know how incredibly painful some of them are for him to think about. Seeing your best friend die is something that sticks with you, forever. Having a fellow crewmember die beside you is something most people would prefer to not remember. Seeing an airplane, or a team, disappear beside you is not a fond memory.
The best advice I might give to you is to have patience with your dad and don't press to hard. If he is ready to talk with you he will, but that may never happen.