Well, without more details, it's hard to say exactly who he is in the context of the ghost story. He could be the protagonist who experiences the ghostly events.
As far as I remember, in 'A Christmas Story' there was no character named Barry. The main characters were Ralphie, his family members like his mother, father, and his little brother. There were also the school bully and the Santa at the department store, but no Barry that I can think of.
Not necessarily. Barry might draw some inspiration from real life, but it's likely to have been embellished or fictionalized for dramatic effect. Many stories like this take liberties to make them more engaging.
Definitely not. Barry is a work of imagination. The plot and everything about it were crafted to tell an engaging fictional tale rather than being rooted in reality.