Short answers, pulled from the story.
The Russell-Einstein Manifesto was released on the 9th of July 1955 during a press conference at Caxton Hall in London. Bertrand Russell presented the document to reporters and world leaders while Joseph Rotblat chaired the meeting.
Albert Einstein signed the Russell-Einstein Manifesto shortly before he died on the 18th of April 1955. His signature provided moral authority to the scientific community speaking out against nuclear destruction three months prior to the public release.
The first Pugwash Conference took place in July 1957 in Pugwash, Nova Scotia. Cyrus Eaton offered to finance this event as the Canadian industrialist who had known Bertrand Russell since 1938.
Eleven pre-eminent intellectuals and scientists signed the Russell-Einstein Manifesto with all signatories being Nobel Laureates except for Infeld. Joseph Rotblat was not yet a Nobel Laureate at the time of signing but later became one.
Joseph Rotblat left the Manhattan Project on moral grounds after learning about the bombing of Hiroshima and seeing an impending nuclear arms race. He remained the only scientist to depart from the weapons program while his peers continued working on it.