"Who would you have called?"
Translation:Vem skulle du ha ringt?
Maybe you already know this, but Swedish movie titles can be a big disappointment. (They very often just use the English title).
And before, when the titles were translated, all movies were called "Det våras för..." ("Springtime for..."). It all started with "Springtime for Hitler" I think and then they just couldn't stop :).
You're on to something, probably this was why they stopped translating titles in the first place. :D
"should" is a huge stretch - the word's been decreasing in usage for a long time. Nowadays, it's perfectly acceptable to use "who" in virtually any context where grammar previously would have dictated "whom". But we do accept both.
"Du" is the subject of the sentence and "dig" an object:
du ringer mig - you call me
jag ringer dig - I call you
If you compare to I (jag) and me (mig), you see the difference in English as well :).