Caroline as a human in fanfiction with Klaus can create a really interesting dynamic. It allows for exploration of how a human might interact with a powerful vampire like Klaus. For example, she could be a source of light in his dark world, constantly challenging his views.
In the fanfic, the pregnancy could be the catalyst for them to truly open up to each other. They might share their deepest fears and desires. Klaus could reveal his insecurities about being a father, fearing he'll be like his own father. Caroline could comfort him and they could bond over their hopes for the baby. As the pregnancy progresses, their love could grow stronger, and they could become a more united front against any threats.
Klaus shows his love by protecting Caroline. He would always be there to save her from any danger, whether it's from other vampires or supernatural threats.
Klaus would be very attentive to Caroline's pregnancy cravings. He'd see it as his duty to take care of her during this time. He might cook for her himself if he can, or take her to the best restaurants to get what she wants. He would be a bit overprotective too, making sure that whatever she eats is of the highest quality and safe for her and the baby. He'd also listen intently to her when she talks about her cravings, finding it endearing and a sign of the new life growing inside her.
Klaus might be overjoyed. He has always been attracted to Caroline, and having a baby with her could be the ultimate sign of their connection. He would probably be very protective, using all his power and resources to keep her and the unborn baby safe.
Their relationship could become more intimate as they bond over the baby. They might start to see each other in a new light, with Klaus showing a more tender side and Caroline learning to trust him more deeply.
It could become more intense. They now have a shared responsibility, so they might be more connected. Klaus might be more tender towards Caroline, and Caroline might start to see Klaus in a different light, perhaps more as a partner rather than just an acquaintance.
Stefan could also play a role. Since he and Caroline are friends and he has a history with Klaus, he might step in to try and stop the marriage. He could try to negotiate with Klaus or find some other way to free Caroline.
There are many. For example, some fanfics focus on their friendship and how they support each other through difficult times in the story's universe. They might explore how Klaus's complex personality affects his interactions with Caroline.
One great 'klaus and caroline fanfic' is 'A New Beginning'. It explores their relationship in a unique way, showing how they might overcome their differences and grow closer. It has some really sweet moments between them that fans of the pairing will love.