What unforeseen event during this conversation works to lago's advantage? What does Othello not
know that would have allowed his to interpret it correctly?

the answer is:  

he is voicing feelings shared by all humans regardless of race.

in paul laurence dunbar's poem "we wear the mask," he replicates the words mask and we to emphasize how people in general -not just black americans- hide their true feelings. he suggests the masks cover people's faces and eyes, which are the main parts that display their emotions. he also thinks people's pain conceal behind those masks, so that they cannot see reality and nobody is able to see one another's sorrow.

walter refusing lindner's offer.

you can't answer this. more information is needed.

that his long years of service outweigh any faults he may have had.

he wanted to be remembered for the good things he did, one of those being when he gave up office so others would follow suit, but george washington wasn’t a man who thought he was perfect, he knew he made mistakes. he was a very talented soldier with a natural gift of tactic.