Hi... Yes it is the right word...

Sure! :) A further thought: how about simply "want"? ie. to be in want, to want for food, as a stronger antonym to "opulence". So you use the florid word "opulence" to describe the riches, and the simple "want" to describe the poverty.

yes you can use it. opulence refers to 'wealth', 'abundance'. so it seems it can be used