Why does nick include Gatsby's story of courtship of Daisy, the information about his war service and his return to Louisville after the war, at this point? What does it reveal about both Gatsby and Daisy?

I think the truth moves bot Nick and the reader. The fact that Gatsby had fabricated some of his past only brings Nick closer to Gatsby. He understands Gatsby better, Gatsby is mortal. I suppose it reveals Daisy's superficiality and Gatsby's illusions/obsessions about love.