What is the ruling on benefiting from what I have read, learned, or seen on the internet, and is it sufficient to seek absolution from my brother to clear my conscience, knowing that I used it stealthily without his knowledge?

A good intention does not justify an unlawful means. Using the network without permission is an aggression that is impermissible if its owner does not permit entry. You must repent and seek forgiveness from the owner of the right, and pay the value of the benefit if he demands it. As for benefiting from what you have read, that is permissible.