Anakin not going to the dark side could have prevented many conflicts. Maybe he would have found a way to peacefully resolve issues instead of resorting to violence. It would have changed the course of the entire Star Wars universe for the better.
Partly. The movie takes elements from various real cases and weaves them into a fictional narrative. So, it's not a direct retelling of one specific true story, but has roots in reality.
There could be a hermit or an outcast Jedi or Sith on Dathomir. Anakin meeting this character could lead to a great revelation. Maybe this character has been in hiding on Dathomir for years, observing the balance of the Force there, and Anakin's arrival disrupts that balance and forces an interaction that changes Anakin's perspective on many things.
He could interact with Luke Skywalker. Imagine Anakin finally getting to meet his son as an ally in the Rebellion. They could train together and share their knowledge of the Force.
Anakin could be angry. He might see his other self as a threat, especially if one represents his dark side and the other his light side. There could be a power struggle between the two versions of himself as they try to assert dominance over the other. Or he could be curious and eager to learn from his other self, about what he could have been or what he can still become.
Anakin could encounter future versions of his friends or enemies from the past. For instance, he could run into a future version of Obi - Wan Kenobi who has also somehow traveled to that future time. Or perhaps he meets a new generation of Sith who have different motives and methods compared to the Sith he knew in his own time. They could challenge his understanding of the dark side and the Force in general.