To answer your questions in order: No, no, and somewhat.

How do we know this? One of the best sources are the Farm Hall Transcripts, the secret recordings of German atomic scientists interned by the British government following the surrender of Germany.

When the BBC announced the atomic bombing of Hiroshima, the scientists (including Werner Heisenberg) were shocked and began discussing how it could have been done and why they weren't able to do something similar. If these men, among the best-informed in the world in the atomic sciences, did not know about the practicality of a nuclear bomb, no one unconnected with the American effort (aside from foreign scientists working on that effort) did.

The American bomb effort was unique in the world because of the cost involved. The U.S. spent about $300 billion (1945 dollars) on the war. Just under 1 percent of that cost was the Manhattan Project. The Manhattan Project was an enormous undertaking -- more than 480,000 people helped produce the bomb. That's one in every 250 people in the United States.

The first bomb, Trinity, was detonated on July 16 in New Mexico. It was a test device rather than a true tactical bomb. The first of those was not ready until later in July. Germany had surrendered in the first week of May. Whether that's "close" or not depends on how close you feel two (almost three) months is.