Now that you have your list of defining moments, choose one of them—something that will be necessary to include in your novel in order for your readers to understand your character—and write the scene of it.
Go ahead and do that now, and then come back to this.
Finished? Now, fact check it.
What did he misremember? Why is it important? How did other people perceive the same moment?
You might not use these facts in your novel. The facts may not matter much, but they will help you better understand how your character moves through her world. It may also help you to understand supporting characters who were involved in these defining moments and how they are understood or misunderstood by your protagonist, and how they, in turn, understand or misunderstand her.
Consider differences in perception and experience. The power of misunderstanding, the ripple effects, the disparities. How what one person finds incredibly profound may be entirely forgotten by another person. And all of this, of course, is to get closer to your character’s experience of his life.