Yes, Criss Angel did sing the theme to his likewise named show, Mindfreak. Angel is an experienced performer, and has released near five albums in his career. Before he was known for his magic career, Angel was the lead singer of the band Angeldust. Criss Angel sings most of the songs on the soundtracks for his show, and performed "MF2," the song for the second season of Mindfreak, with Sully Erna of Godsmack.
No, Darren Criss is not bisexual. On Fox's TV show Glee, his role as Blaine Devon Anderson is engadged to Kurt Hummel, they got engadged in season five episode one. His role on Glee is for him to play a gay role, however he is not gay. He is straight, he has a girlfriend named Mia Swier who is in a band called, Guns And Hoses.
Sarah Thompson's character in Season Five of The WB's "Angel" is said to be the girlfriend of the in-hiding Lindsey (Christian Kane). Although they were a 'couple' it is obvious that Lindsey was just using Eve to get at his arch-nemesis, Angel, which led up to the 100th episode, "You're Welcome". Her fate is unknown in the series finale.