Getting his death certificate might be the next step, although California is making it more difficult now than it was a few years back. Now you have to have your request notarized, proving that you are indeed who you say you are...
I asked about a prior marriage because I was wondering if the "Mother" or "Mother in law" from the 1920 and 1930 censuses for George Cook and his wife Mary is the correct Maud Forsyth. Could she have had a daughter Mary in England who then married George Cook? That Maud has the correct name, middle initial and birth date, but the death record for George and Mary's daughter Frances says "Mother's maiden name Forsyth" which would not be the case since Benoni and Maud weren't married at the time of Mary's birth (abt 1890). Unless of course Benoni was actually her father (as he seems to be the father of so many others...!)
Now here is an interesting thing: In the two censuses listed above Mary Cook says she came over in 1911. A Mary Forsyth arrived in New York on 19 Jan 1911, going to her mother at 412 East 60th Street, New York. She says she was born in Maidenhead in 1890. Nearest relative from whence she came is Mrs. Roberts, 5 West Street, Maidenhead.
Mary is a hospital nurse.
Mrs Roberts at 5 West Street, Maidenhead in the 1911 census turns out to be Lucy Elizabeth Roberts, born 1852 in
Lowestoft, Suffolk!! Lucy Elizabeth Holbrook married Arthur Wells Roberts in 1872. She is Maud's sister.
I am convinced that the Mary Forsyth who married George Cook is the daughter of Maud and that it is your Maud who is living with them in 1920 and 1930 in Manhattan.
No idea who Mary's father was, though, or by what name she was known before her mother married Benoni. I don't see her as Mary Forsyth in 1901 or 1891.
All the best,
Sarah
P.S. In this case, I would bet that the death found for you on italiangen.org by another researcher in the link I gave above is the correct one:
Maud Forsythe - 69 years Jul 20 1931 18361 Manhattan