Joe Gannascoli (Vito) made his character's arc?

Watching an interview and Joe Gannascoli says that he came up with Vito being gay after reading a book. I'm curious to know what book he was referring to?

And if he did come up with Vito being a fanook, why was he so upset with his character ultimately being killed off? It was almost a given considering the life he was in, and refusing to leave it behind to stay in Massachusetts with Johnny Cakes.

It's interesting because from what I've heard, writers had control of the story and actors weren't allowed to add their own stuff in (with the exception of Furio and Paulie)