Did she or didn't she

1. They were not on a list for a court martial. They were on a list of pilots whose leave had been cancelled, and they were to report back to base immediately, which means drop everything and leave at once when you are shown the orders. The sentence about failure to comply would result in court martial was the standard, but stern warning and reminder to leave immediately, not hang around for a few more hours of fun. Jack was not in violation because he didn't see the orders until the two MP's showed up at the hotel room.

2a. Jack was drunk and on leave, and was only paying attention to hot chicks in dresses. When Mary approached in uniform, he only reached back and felt the uniform, and didn't bother to turn around and see who it was. Yes, normal red blooded males can be turned on by chicks in boots and belts and uniforms. However, for a soldier who has been at the front for months and is now on leave, the LAST thing he wants to see is a uniform. He'll take the slinky dress over a uniform in a heartbeat.

2b. No clue.

3. Typcially, there's lots of "immoral" behavior in war settings, and most of it is not punished. If it causes an incident of some kind or causes embarrassment to the service, that's when people start getting shipped out. Mary getting shipped home in the story was probably done more for the sake of the audience and not offending them, as opposed to an acurate reflection of what would have happened.

4. No. Jack was so drunk that he didn't even recognize his best friend from home. And so drunk that he was more interested in watching imaginary bubbles than getting busy. He passed out on the bed, and Mary was starting to change into her uniform when the MP's arrived. As far as the near nudity is concerned, remember that this film was made before the Production Code started being enforced (mid-1934). It was not too unusual for films before then to have some near nudity and/or obvious sexual references, and on rare ocassions some actual nudity.
That's part of your problem, you haven't seen enough movies. All of life's riddles are answered in the movies.

From what I have seen in photographs, American nurses dressed similarly to British nurses -- loose dresses, bib aprons, veils or caps.
However, Mary was NOT a nurse. She was an ambulance driver. Many American and British women served as ambulance drivers, transporting the wounded from the front to hospitals behind the lines. The drivers' uniforms were different: mid-calf skirt, boots, jacket, along with belts, buckles, and brass buttons. They don't seem to be that different from the uniforms worn by the "hello girls," female telephone operators, preferably ones that spoke French, who worked the telephone switchboards along the American front.

Seeing Mary in uniform while on leave had no effect on Jack. He had grown up with her and she was still "on of the guys." Which is why she resorted to the fancy dress, at the suggestion of the restroom attendant. This caught Jack's attention -- he had never seen Mary dressed this way before -- and got him away from the French girls.

No, Mary and Jack didn't do anything. Jack passed out before anything could be consumated. Women in service being sent home for immoral behavior is not inconceivable. (I am a Civil War scholar and as far back as the 1860s, nurses and women in contact with the military could be dismissed for sexual indiscretions.) If you watch the 1932 Gary Cooper/Helen Hayes version of "A Farewell to Arms," British volunteer nurses were sent home for the very same reason. That such happened to Mary is a double standard, but no surprise.

Sorry for such a long response, but I am a history and film geek.

Spin

1) It's possible that they were required to keep themselves available or in contact just in case. I don't know if that counts a trip upstairs with the ladies.

2a) She had to compete with the other Parisian sirens to get his attention.

2b) Don'tknow

3) Will look into this. =8^ )

4) Don't think so, she was a 'good' girl and was trying to keep him from making a drunken mistake with strange women. She just wanted to get him out of there. Of course the situation of being caught with a man in a bedroom meant instant guilt. (Not for the man, though)