The coordinating conjunction among these is the word but.
However and although are subordinating conjunctions, not coordinating.
I am not sure what you are asking here. If you are asking what parallel structure looks like, you would have to keep the verb tenses the same. For example, Sam likes to ride bikes, hike trails, and bake bread. What is does NOT look like: Sam likes to ride bikes, go hiking on trails, and baked bread with her grandmother. The structure words would be based of the passage you were given, which isn't supplied here. If you were asked to write a paragraph using a parallel structure, follow the example given here.
Johnson uses sarcasm in this poem as he expresses the opposite of what he means. When he says "pile on the Black Man's Burden", and gives examples of how people can make black men more miserable than they already are ("his wail with laughter drown"), he is using sarcasm. He clearly does not want people to pile on this burden and make black men's lives harder, but he is saying that people should do it to show them how ridiculous it sounds and to point out that people are already doing that.
B, removing American Indians will allow white settlers to become wealthier
He declared that they were still barbarians and that trying to understand them has been a failure because the government often slaughtered its own policies or they failed. This is why it was acceptable to exclude them from their territories since they were still savages according to him, and the rest of what resembled to the Native Americans is history.
