1) I think it’s saying how you get what you give. Like the more you give in life the more you will get. 2) not sure maybe they are trying to say they are clueless 3) maybe like he is trying to shine a light on the times when he is struggling(can’t see in the dark). I believe it’s a metaphor for how there are dark times and he is trying to shine a “light” through that.
I would go with D) It helps show the author's voice because the author is saying that the person is making him sad at night so u could say he is opening his feelings.