"Mara, does Torg understand?"
Translation:mara, yaj'a' torgh?
I understand why you think that, but in this course we use the assumption that the original sentence has been stated in a specific order for a reason and thus, if the grammar does not require you to change the order, then the parts should be maintained in the same order. Since in both languages you can call the name first and then ask the question, then that is what you should do in the translation as well.
This also has the added benefit of breaking the habit of just reading the sentences from the last word to the first word, since when speaking the language you can't do that.
Sure, in the sense that "knife" is in the instrumental case in the sentence "he cut the bread with a knife".
I don't think it makes any sense to posit a vocative case in English or Klingon, because words never look different in this vocative case than in the nominative case.