Plot hole: The idea that Marlow would simply take a taxi to his wife's address after being missing in action for thirty odd years is stupid beyond belief. He was on a ship sailing from the central Pacific for days and those ships have radios! The US military would have known he was coming. Someone, somewhere would have notified the authorities that a US serviceman long thought dead was actually alive and on his way home and his wife and son would have been there on the docks to greet him, not standing slack-jawed in the kitchen dropping trays of drinks on the floor when he turned up! What would have happened if she had remarried? Or moved house? Or she was dead? Don't tell me the US military didn't know he was coming - he is wearing a brand new uniform, clean and pressed.
Character mistake: Chapman is wearing a gold oak leaf cluster insignia on his uniform which is the rank of Major. At the initial briefing he is introduced as Major, which is correct. Throughout the movie he is referred to as Captain, which is wrong.
Suggested correction: He is referred to by his name "Chapman"; it sounds close to "Captain."
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