Terror stalks theater stages in Connecticut this fall with three “Draculas,” two “Sleepy Hollows,” two “Droods,” a “Hocus Pocus,” a “Carrie,” a “Rocky Horror” (of course) and one more “Sweeney Todd.”With all those titles floating around, you begin to notice how dark some of the offerings can be as well. Take the splashy flapper-era panic “Gatsby.” It’s a big shiny song-and-dance musical with a jazzy score and lots of wild partying. Yet on some level it’s also a murder mystery and a crime drama. The F. Scott Fitzgerald novel “The Great Gatsby,” on which the “Gatsby” musical is based, is...