One common theme is the exploration of different fighting styles. Since Steve Fox is from a fighting game, crossovers often involve him interacting with characters with different combat techniques and then learning from each other.
Sure. You could try looking on fanfiction.net. There are often some great Steve Fox crossovers there. Just search for 'Steve Fox crossover' in the search bar, and you'll get a list of relevant stories.
I don't know who Steve Crisp is in this story without more details. He could be an ordinary person with an extraordinary experience, or someone with a special talent.
On the other hand, Steve might be more understanding than expected. He knows about Bucky's past traumas and could suspect that something else is at play. So, instead of immediately resisting, he might play along for a while, waiting for the right moment to figure out what's really going on and how to help Bucky.
You can start by looking on Archive of Our Own (AO3). It has a large collection of fanfictions, including ones about Steve and Tony. Just search for the relevant tags and you'll likely find many great stories.
In the context of this fanfic, Catherine Rollins and Steve are likely characters created by the fanfic author. They could be original characters, or they might be based on existing characters from a particular show, movie, or book. Without more context, it's hard to say exactly who they are other than two individuals whose relationship is central to the story where Catherine makes Steve cry.
I'm fairly certain that Steve is not a character in 'Pulp Fiction'. The movie is known for its complex and intertwined storylines involving a relatively small number of main characters, and Steve is not one of them.