Why did Malcom dress as a clown before taking Cliff's place in the air show? I don't think anyone would have seen him either way.
Because it was part of the act Cliff was supposed to do. Malcolm is Cliff's friend, and he's going to do what he can to help him.
Isn't the use of Uniformed Commandos on American soil technically an act of war? Admittedly neither the US nor Nazi Germany has the means of fighting a cross Atlantic war. But surely a diplomatic row would ensue?
Not even technically. It IS an act of war. Especially when combined with the video that clearly outlines the Nazi plan to invade and conquer America once they steal the rocket. Normally such a thing would lead to an immediate declaration of war, but the Feds decided to cover it up for now. I guess because they weren't ready to reveal the existence of the rocket to the general public just yet. Not until they had one of their own to play with, at least. So either Howard Hughes and Peevey took the secrets of the rocket pack to their graves and history continued as normal, or WWII took a turn for the Crazy Awesome.
Why did the Nazis play scary music in a cartoon made for their own soldiers that was supposed to depict their victory?
It's meant to be inspiring, in a Wagnerian way, but without actually being Wagner.
Why doesn't the exhaust flame of the rocket pack Burn Cliff or Neville's legs off. I get that the pack itself has a cooling feature to keep it from exploding on his back but that doesn't excuse the flames being long enough to reach his pants without them catching on fire.
Shh! You're not supposed to notice that!
Actually, if you look closely, you can see two heat-shields just below the exhaust nozzles of the rocket pack, which would indeed protect the operator's legs.
Why did Neville Sinclair have a walk-in closet full of women's dresses in his house?
For all the women he brings home, duh. Take a poor girl home, dress her up like a doll, a bit too much wine...
Far better - and infinitely creepier question: why did he have chloroform with him on his date?
only marginally better, maybe he was intending to use the date as cover for a operation of secondary priority, maybe someone in the region was on a list of targets of opportunity for some reason?