No, Snape loved Lily Potter (Evans). Harry's mother.
Yes, and he never tried to disguise that. But he loved Lily Evans/Potter.
Lily Evans and James Potter. I'm obsessed with the series. :)
Yes, with Lily Evans.
He loved Lily Evans (Harry's mother), but she only considered him a close friend. She was his only real friend; they had become friends as children. Snape's love for Lily - in spite of her marriage to James Potter, whom Snape despised - was his motivation to become a double agent for Dumbledore when he learned that Lily was marked for death by Voldemort.
Snape never married anyone. He was in love with Lily Evans from the time they were children, and never got over her marrying James Potter.
Lily Evans.
Wizards' Patronuses can sometimes change shape. Severus Snape loved Lily (Evans) Potter and so his patronus changed shape to the same one as Lily, a doe. It is very likely that Snape's patronus didn't actually change shape and was always a doe since he had loved Lily all his life.
Yes, Severus Snape was always in love with his childhood friend and Harry Potter's mother, Lily (Evans) Potter. Snape ruined their friendship and any chance for a relationship due to his involvement in the Dark Arts, which led to him calling Lily a mudblood. This is a large part of the reason why Snape hates Harry's father, James, who frequently bullied him throughout his school years and then ended up with the woman he loved.
Lily Evans, who later became Lily Potter.
J.K. Rowling said in one of her interviews that Lily "might have grown to love [Snape] romantically, had he not loved the Dark Arts so much." So, her falling in love with him was a possibility, at one time, but he ruined it by immersing himself too deeply into the Dark Arts.
No. Never in the books but there are plenty of fan fiction stories in which they are romantically involved.