In regards to question 3, Chekhov gives the appearance that he is merely informing the readers (us) of Gurov's reasoning behind his actions, not defending him. If a man was beating his wife, you could bring certain circumstances to light without giving him a true excuse. Chekhov portrays Gurov's wife to be cold to him, while at the same time showing the suavity of the husband himself. While these paint a picture of what led Gurov to pursue extramarital relationships, they don't necessarily exonerate him from the actions. With the inclusion of his failed marriage, he becomes more than the standard archetype of "the cheating rat bastard husband". As always, point of view is very important in any piece, and doubly so in this story. The use of third person takes away the personal slants that would have been implemented if it was told through the eyes of Gurov himself. What we are given (hopefully) is a truthful portrayal of Gurov, His motives, and His characteristics.
When it comes down to it, we can read into the intentions of Anton Chekhov all day and guess what he was trying to accomplish. Personally, I'm satisfied by adhering to the words of Mark Twain: Persons attempting to find a motive in this narrative will be prosecuted; persons attempting to find a morale in it will be banished, persons attempting to find a plot in it will be shot.