1) When did the term 'gesundheit' start being used in America? Would an American feasibly use that slang in the 1940's, or would that be pretty much taboo, considering the war? I've tried looking up 'gesundheit etymology in america' and 'gesundheit slang in america 1940s' and a few other variations, but haven't come up with anything.
2) I've found some pretty good sites that basically answer this question, but I'd like to clarify some finer points about it: How do you say 'I'm sorry' in German? Google tells me that 'Es tut mir Leid' is the general/informal way of apologizing and that 'Entschuldigen Sie' and 'Verzeihung' are formal ways, but would that be considered formal in terms of speaking to someone who is above you (like a boss or a higher-ranked officer) or simply formal in terms of speaking with someone you respect/don't know?
Edit: The context of the apology is the Nazi apologizing to the American for the whole situation (because it's his fault the American was hurt at all); he's doing so reluctantly (because they're archenemies) but sincerely. I'm probably gonna go with 'Es tut mir Leid.' :)
3) How would someone say the full sentence 'I don't give a damn'? I was looking up German sayings on Google and came across 'Keinen Bock,' which the site said was 'not give a damn.' I've used an online translator (which gave me something completely different), searched for 'how to say I in German,' 'how to complete sentences in German,' and 'how to say I don't give a damn in German,' but the best I've gathered is that maybe 'Ich Keinen Bock' would be right. Is it?
I really appreciate any help you can offer!
Edit: Holy wow, guys, thank you so much for all of your help!