Another possibility is that he would try to bring her back to life. Given his knowledge of the vampire world and any possible supernatural elements in the fanfiction universe, he could explore dark magic or ancient vampire rituals. He might go on a quest to find a way to reverse death, driven by his undying love for Bella.
Edward might seek revenge if he believes Bella's death was caused by someone. He would use his vampire abilities to track down the supposed culprit. For example, if he thought a rival vampire or a group of humans were involved, he'd be relentless in his pursuit. His sense of loss would fuel his anger and drive for vengeance.
In some fanfictions, Edward might be initially shocked. He could be worried about Bella's health, considering the unique situation of a human - vampire pregnancy. He might also feel a sense of protectiveness towards Bella and the unborn child, and start making plans to ensure their safety.
He might be completely devastated. In many fanfictions, Edward enters a state of deep despair. He could isolate himself from others, feeling like his world has ended without Bella.
His relationship with his family could become strained. They might try to comfort him, but he could push them away in his grief. For instance, Alice, who usually has a close bond with Edward, might find it difficult to reach him as he closes himself off.
They could be very protective. After all, Edward is their son. So they might be a bit cold to Bella at first, sizing her up.
Jacob might feel extremely angry. In the Twilight series, Jacob has strong feelings for Bella. Seeing her kiss Edward would be like a slap in the face. He could feel betrayed and might even lash out at them.
Bella would likely be very frightened during the car incident. Once Edward saves her, she'd be extremely relieved and probably feel even more attached to him. Edward, on the other hand, would be initially worried and focused on getting Bella to safety. After saving her, he might feel a sense of relief as well, but also a bit of that over - protective feeling that he often has for Bella.
Well, Edward could start to distrust Bella completely. He may constantly question her every move and word, leading to a lot of arguments between them. For example, he might not believe her when she tries to explain things. This could also cause a rift in their relationship with other characters, like their vampire and werewolf friends who might get involved in the drama. The whole dynamic in their fictional world would change, with a lot of tension and unease.
One possible reaction could be shock. Carlisle might be momentarily stunned to see them in an unexpected situation. He could quickly compose himself and offer some words of wisdom or caution. For example, he might remind Edward to be extra careful with Bella considering her human nature.
In fanfiction, Edward's reaction could vary greatly. Some stories might depict him as being overjoyed and excited, ready to embrace fatherhood. However, considering the unique situation of a vampire and a human having a baby, he could also be very apprehensive. He may think about how the baby will grow up, whether it will be accepted in their world. He might also be concerned about Bella's transformation, if that becomes necessary for her survival during or after the pregnancy.
I would recommend 'A New Beginning for Bella and Edward'. This fanfic takes their story in a different direction after the events in the original series. It shows how they handle new challenges together and the growth of their love in the face of those difficulties. There are some really beautiful and heart - warming moments in it.