Mark Grayson isn't Asian. The creators of the comics have established his ethnicity as something other than Asian. This is a well-defined aspect of the character's portrayal.
Hard to say. To determine if it's a true story, we'd need to know more details about the origin and sources related to Jennifer Grayson. Sometimes stories are inspired by real life but have fictional elements added.
Mark Grayson isn't Asian in the comics. This aspect of his character has been consistently portrayed throughout the various comic storylines and depictions. There's no indication of him having Asian ethnicity.
I haven't come across any reports stating that Jake Tapper is penning a novel. His focus seems to be on his journalistic endeavors, such as reporting the news, conducting interviews, and providing analysis. However, it's not impossible for him to venture into novel - writing in the future, but for now, there's no indication of it.