I passed up the chance to see The Sound of Music performed on a tiny stage at a community theater. I should have gone! It would have been like a 3D movie. But I have sympathetic stagefright anyway and with them singing as well as acting, it would have been too much for me.
Now it's going to be on live TV.
The grim reality was that Maria didn't love her husband when she married him (she said she loved him later). She wanted a husband and he wanted someone to take care of his huge family. He wasn't rich---he had lost all his money in bad investments which is why he didn't object to his children performing in public. They needed the money.
Poke around on Wikipedia. You can find the name of the submarine that Captain Von Trapp commanded in World War One, and you can see a list of the ships he sank, although they don't give the death toll.
They didn't flee. The Nazis weren't trying to force him into the Navy. The family just happened to move, and they returned to Austria several times during the Nazi era without any trouble.
It would be interesting as the lurid story of a defrocked nun hired to care for a bunch of neglected children whose rigid authoritarian father runs their household like an Austro-Hungarian submarine. The teenage daughter dates an admirer of Adolf Hitler. The children have a pathological fear of thunder. The captain's wealthy fiancee tries to get rid of the fallen nun but fails and is forced to flee.