Haru does love Legosi in the manga. It's evident in the way she cares for him, shows concern, and their shared experiences strengthen their bond, making it clear that her emotions towards him are those of love.
Partially. The core idea and some elements of Juno draw from real experiences, but it's not a completely factual account. The filmmakers took creative liberties to shape the story for the screen.
Sure, Legosi and Haru do get together in the manga. Their relationship develops over time, facing various challenges but ultimately finding their way to each other.