Is the reward for one who teaches Islamic sciences in a small society equal to that of one who teaches Islamic sciences in a large institution, if they are equal in effort? And does the transformation of the society into a large institution affect the reward?

No one knows their equality or superiority in reward except Allah. It is apparent that a servant's reward is magnified in proportion to their sincerity and devotion. A small deed may surpass many if accompanied by sincerity and truthfulness, as in the hadith of the dirham that outstripped a hundred thousand dirhams, and the man who removed a thorny branch from the road, for which Allah forgave him. A single deed may be performed by a person with complete sincerity and servitude, and Allah may forgive their major sins through it, like the case of the man with the card who said "La ilaha illallah" (There is no god but Allah) with sincerity, so his good deeds outweighed [the bad], and the man who gave water to a dog, and the harlot who gave water to a dog, and the man who removed a thorny branch. Deeds vary in merit according to the variations in faith and sincerity within the hearts. "Never will their meat reach Allah, nor their blood, but what reaches Him is piety from you." For this reason, the standing of two men in a row might be the same, yet the difference between their prayers is like that between the heavens and the earth.