For #1 (Dissociative Identity Disorder) -- This is the Sun Gone Down (http://dark-reaction.livejournal.com/120803.html) by dark_reaction

Amazing AU piece from Dean's point of view. The beginning (well, the second and third paragraphs, actually.)

Dad didn’t notice, saw them as outbursts and temper tantrums and not for what they were. Dean knew something was very wrong years before he could put a name to it. One moment, Sam would be smiling, sweet and finagling and the next—he'd be cool, distant, and older in his body, older than Dean.

The writing started, snatches in a hand Dean didn’t recognize—notes that didn’t make any sense, and never where Dad could find them. The shifts in Sam’s personality scared him, like an iron-fist bearing down on Dean’s heart. Over and over and over and over. Please let him stop acting like this. But he never did.