If I were still teaching, and wanted to show a movie about the war in Vietnam, I don't know what I'd do. I don't think there are any particularly accurate movies about that war. The Deer Hunter is the great masterpiece to come out of that war, and while John Ford would likely have approved of it, had he lived to see it, it is more a work of poetry than history. As for WWII, based on my late uncle, who served in WWII and Korea, and who used to speak of the tedium, I would think that the one movie that best captured what those servicemen who survived the war experienced, would be Mister Roberts.
The Devil's Brigade might have been made because of The Dirty Dozen but it is pretty historically accurate as well, right down to the final assault on the mountain in Italy. They were made up of misfits from Americans and crack Canadian troops; and yeah there was a lot of Hollywood (like the training and brawling) but a lot was fairly accurate, too. The First Special Service Force never retreated and never lost a battle, but they took heavy casualties and were disbanded before the end of the war due to attrition.
That depends on the service member, I would guess. I never knew that my wife's dad had a DFC and two bronze stars with "V" Device for valor until I literally stumbled across the awards cleaning out his garage. The old guy flew with "Pappy Boyington" and the Black Sheep. Also served in Blackburns Irregulars the sister squadron. His DFC says he attacked forty zero's by himself knocking down eight in the first ten minutes until help arrived. Doesn't sound like a lot of tedium to me. Shot down twice fished out of the drink by a sub both times. He never said a word and refused to discuss them with me until I got him a little tipsy one night. That to me, is the epitome of the word "hero."