The dates in the writer's email seem to agree with Harvey Fuller's "Nevada Gambling Establishments" publication (which may be where Anderson got his info).

In Q#4: The location may have been closed between the California Club and the Friendly Club. I don't know of any intermediary club.

In Q#6: Yes, there were 3-4 casinos per block downtown in the "old days". Same situation across the street at the Golden Nugget, which had 3-4 casinos on that side of the street at times. See some of the old postcards/photos of downtown to help visualize how these casinos looked.