Well, 'In the Shadows of Abuse' is an interesting 'abused Severus fanfiction'. It not only portrays the abuse Severus suffers but also how his relationships with other characters are affected by it. 'Breaking the Chains' is also worth reading. It's about Severus breaking free from the cycle of abuse and finding his true self.
There is a story called 'A Severus Reborn' in the 'abused Severus fanfiction' genre. In this, after enduring abuse, Severus discovers new strength within himself and uses it to change his fate. Also, 'Hidden Pain' is quite popular, as it focuses on the psychological impact of the abuse on Severus.
First, Severus would probably try to gain Harry's trust. He would do this by being less harsh on him in class and showing a bit of kindness. Then, he would try to find out more details about the abuse without scaring Harry away. He might enlist the help of some of the more trustworthy students, like Hermione, who could also keep an eye on Harry. Severus would also make sure that Harry has access to any resources he needs at Hogwarts, such as a warm place to stay during holidays if he doesn't want to go back home.
One popular one might be 'A New Start' where Severus discovers the extent of Harry's abuse and takes him under his wing. He provides a stable home and helps Harry with his magic studies in a more nurturing way than at Hogwarts. It's a heartwarming read.
James might be shocked at first. He could then feel a sense of protectiveness towards Severus. Maybe he starts to see Severus in a new light and tries to find ways to help him, like keeping an eye on those who abuse Severus.
Severus is a very observant character. He may notice that Harry has a lack of certain basic skills or knowledge that a normal - cared - for child would have. For instance, Harry might not know how to handle simple social situations in a healthy way or might be overly defensive. This could lead Severus to suspect that Harry's home environment, where he should have learned these things, is not a healthy one and that he might be suffering abuse.
One common theme is his relationship with Lily. Writers often explore how his abuse might have affected his feelings for her and how it influenced their interactions. Another theme is his time at Hogwarts as a teacher. How his past abuse made him act the way he did towards students, like Harry.
You can start by looking on fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'abused Severus Snape' in their search bars. There are often many different takes on this theme, from exploring his childhood abuse to how it affected his relationships later in life in the context of fan-created stories.
Well, Severus could be quite sneaky about it. He might start observing Harry more closely in the corridors and classrooms. If he notices signs of abuse, like Harry being overly withdrawn or having unexplained injuries, he could enlist the help of other trustworthy faculty members. He might also try to give Harry some extra tasks or projects in Potions class to keep him occupied and away from his thoughts about his family situation. This way, Severus can gradually build a relationship with Harry and offer him some form of support without making it too obvious at first.
He would become more nurturing. Usually, Severus is seen as cold and aloof, but with Harry in his care, he'd have to show more warmth. He might still be strict, but it would be out of love for Harry's well - being rather than just being his usual harsh self.
There's also 'The Unlikely Bond'. In this fanfic, the OC is a healer who ends up getting involved with Severus. It shows their relationship growing from distrust to a deep connection, and it's full of interesting magical elements and character - driven plotlines.
One great Hermione and Severus fanfiction is 'A Different Sort of Magic'. It explores a unique relationship between them where they collaborate on a complex magical research. Another is 'The Unlikely Bond' which delves into how their different personalities gradually find common ground.