Dolly Parton’s nearly 60-year marriage to Carl Dean was unconventional, as her husband largely remained out of the spotlight. Randy Schmidt, who worked on “Dolly on Dolly: Interviews and Encounters with Dolly Parton,” told Page Six in an exclusive interview, “Dolly and Carl certainly had an unconventional marriage, but it seemed to work beautifully for them. “In the early years, she spoke quite candidly about the freedom they gave each other and the fact that they each lived very independent lives. Some of those comments weren’t particularly well received by her fans, and I think she eventually learned to keep that part of her life much…