Until 1973 homosexuality was considered a psychological disorder american psychological association. which sociological perspective would be most concerned with why this was considered an illness, and what effect that diagnosis had on society?

The answer is Symbolic interactionist.
Symbolic interactionist refers to a sociological perspective which attempts to understand how individuals interact with one another using symbolic gestures and how it could contribute to the formation of pragmatism method to analyze social situations (such as same sex relationship)

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.