Some streets have multiple names, e.g. "Avenue of the Americas" in New York City. Some streets have names that change with surprising frequency as you proceed down them. If the officer used a street name that is confirmed by MapQuest, odds are it's a valid street name. Note, the street name does not affect an estimate or measurement of the velocity of your car.
The fact that the officer pulled you over at a different spot than where the officer observed you speeding is not a defense to a ticket. You can argue that it would have been impossible for the officer to read your license plate before pulling you over; I expect that the officer will deny having any difficulty identifying your car as the one he observed speeding.
Perhaps one of the Washington ticket gurus will comment on possible defenses, including the radar certification issue.

