I rely entirely on my feel of the language (I'm not a linguist though) and literature. Nabokov's novel begins in the country, somewhere in the province of St. Petersburg, not too far from the place where the Nabokovs' Vyra estate is situated (about midway between Petersburg and Luga). On the other hand, there really existed a minor writer Lugovoy, who took his pen-name after Luga and who partly might have served as a model for Luzhin pere. 

As to Dostoevsky's novels, practically all of them are set in the city. Incidentally, because most surnames come from professions, the name Luzhin can come from ludit', "to tin". Readers with a hypersensitive ear can also discern lozh', "lie", in that name (Dostoevsky's Luzhin turns out to be a lier).

Sorry, if I don't answer all of your questions (or if my answers are a bit off theme). I do not risk it because my English is limited and you ask too many questions.