It could be that those stories hold a great deal of significance for them. They might be trying to pass on important lessons or values that they learned from those experiences, so they keep repeating them.
Not necessarily. Even if it's a true story, some people might be skeptical. There could be various reasons for this. For example, if the story seems too extraordinary, or if the person telling the story has a reputation for exaggerating in the past. Also, people's own biases and beliefs can influence whether they believe a true story or not.
No. People have different levels of trust. Some may be more cynical and doubt the truthfulness of any story, regardless of whether it's true or not. Also, if you have a reputation for exaggerating, they might not believe your true story.
No. There's no way to verify if every single story he tells is completely true. He might be exaggerating or making some parts up for entertainment purposes.