On the contrary. Paul was not married. He actually endorsed celibacy for those capable of it: "To the unmarried and the widows I say that it is well for them to remain single as I am. But if they cannot exercise self-control, they should marry. For it is better to marry than to be aflame with passion" (1 Corinthians 7:8-9).
Perhaps, but we know that he said “men and brethren, I am a Pharisee, the son of a Pharisee” (Acts 23:6) and that Pharisees were required to get married. Did his wife died? Was she left behind in Jerusalem while he went on his trips?
Conceivably he had been married at some point and his wife had died, although there is no evidence for that. I think it is more likely that he never was married, but I don't think we can rule out his being a widower.
When he tells Titus that a bishop should be the husband of one woman, I would take that as excluding men who had remarried after their first wife died.