Trivia: Kong has only 14 minutes of screen time in the entire film.
Trivia: The line "Hold on to your butts" said by Samuel L. Jackson is also said by him in Jurassic Park.
Trivia: The helmet with the line "born to kill" and the peace and love sign from the film Full Metal Jacket is seen in the movie.
Trivia: The fight between Kong and the octopus is reference to the movie King Kong vs Godzilla from 1962.
Suggested correction: The implication is that Marlow went through an extensive debrief and nobody had contacted his family until the debrief had concluded, based on the top secret nature of the mission. As you say, the fact he has a brand new uniform suggests that he has contacted the US Military prior to ever contacting his family. The fact that his wife would have moved and re-married is irrelevant, he still would have made an attempt to contact her so he could see his son.
BaconIsMyBFF
And they wouldn't have contacted her after the debrief had been completed? What utter nonsense. Allowing him to just turn up on the doorstep without notifying his wife first is an utterly irresponsible and even dangerous act. She could have fainted with shock or even had a heart attack. She would absolutely, definitely, 100% carved in stone, been advised of her husband's survival and return.
Since we know very little about the completely fictional organization Monarch, we obviously cannot say they would "carved in stone" do anything. In order to be a mistake in the movie, it would have to be something that is impossible. A secret government organization that doesn't even exist in real life not behaving the way the real military would is not impossible. At least not by the rules set forth in the film. It's perhaps improbable but it is most certainly not impossible.
BaconIsMyBFF
It is an inviolable, carved in stone, fur lined, ocean going, top of the list rule that the next of kin are immediately advised of the change of status of military personnel. MIA, now confirmed dead? They'd be the first to know. MIA, now confirmed to be alive, same outcome. His wife would know he was on that ship coming home.
This is true in real life but in the fictional world of the movie Monarch is a secret, government agency that has some degree of control over the military. You can't apply the same rules as in real life in this situation.
BaconIsMyBFF