As I see it, the only line that makes up a rhyming couplet is C."So I stared at the Night! And she / Stared back solemnly at me!". Well, it’s easy to catch the beat, you just need to read all the words aloud with pauses and all the punctuation marks. In that case we have two rhyming words, they are ‘’she’’ and ‘’me’’, you need to focus on the pause after ‘’she’’ and everything will be clear.
For the question it is unsure because according to the question it is unquestioned so your welcome
The correct answer in this case is "we"
Us is also correct but in that case the sentence would not be an elliptical one. If you use "we" then the sentence is both correct and elliptical which fits the description of the question.