Here are the sources for my research.

RMS Lusitania passengers and crew, the final return of those on board. Dated 1 March 1916. (The notes in the list are mine)
Second Cabin

Crew list for the Lusitania held at the National Archives, London (This is where the individual crew members signed on the ship’s articles; it is also noted whether they survived or not; note ”paid off” and ”supposed drunk vessel sunk” on the right hand side). Their individual salaries are also noted.

Lusitania sign on

Census for England; 1851-1911 (mainly 1901)

Census for the USA; 1880, 1900, and 1910

Various newspapers, notably Boston Daily Globe shortly after the sinking

LDS Family Research Center

‘Wilful Murder. The Sinking of the Lusitania.” Diana Preston, 2002 (ISBN 0385601735)

The Lusitania Resource web page

Merseyside Maritime Museum; the Lusitania section

Individuals; notably Geoffrey Whitfield and Jim Kalafus