Definitely not. John Diggle and Green Lantern are distinct entities in the comics. Green Lantern has specific powers, origins, and adventures that are separate from those of John Diggle.
In some comic storylines, Andy Diggle and John Diggle are related. But it varies based on the creative direction and the specific context of the comic series. It's not a consistent relationship across all comics.
Sure, John Diggle is in the comics. He's often involved in action-packed scenarios and has connections with various characters. Sometimes his comic version has different developments compared to adaptations.
I'm not sure if there is a specific fanfic directly related to 'bald John Green' and 'other John Green'. There are a vast number of John Green fanfics out there, but this combination seems rather specific. It might exist in some corner of the fanfic world, but it would take some in - depth searching through fanfic platforms to find out.
Green Arrow isn't typically portrayed as an asshole. He's often a hero with a strong sense of justice, but like any character, he has his flaws and moments of difficult choices.