Cat, I've been following your 'search' as I've found it interesting. Your family has certainly given you a good chase, so to say.
I believe your Frank (s/o John Edwards/Elizabeth Davis) is living with Elizabeth Jackson on the 1880 census. Just as Una seems to be living with a grandparent, so does Frank. He's age 12, listed as grandson in the home of Thomas Jackson in Eau Claire Co WI.
Also for the 1900 census in , it gave me a bit of fits and took a while, but John Spohn and wife Elizabeth are on it with two children: Arthur J born March 1877 and Loretta (I thinkj s your 'Etta') born July 1880. Papa John born Oct 1845 and Elizabeth born Nov 1848 both born IL. It's in index transcriptions as 'Shaker' though image appears to be 'Spohen'.
This census also gives the couple as married 26 years, so being about 1874.
I believe that your Elizabeth does appear in Cook Co IL census for 1850 as Lydie age 2 born IL in the home of John Edwards age 26 born England and 'E' age 22 born England. They are living next to a John age 46 born England...I'll let you decide what image says for John's last name but it appears it says Barrell or bartlet or somehting inbetween.
I did find a family tree maker that states that suggest John Edwards went to California (minus his wife) for the 'gold rush' and after like seven long years he returned and she divorced him. Of course I've no idea if that scenario is accurate but you might look for divorce records between 1850 and 1857.
It goes on to state that Elizabeth (Barrell) Edwards then married Thomas Jackson and they moved to Wisconson. I could not find a Edwards/Jackson marriage in Cook Co IL index in the IL Marriage Rolls from IL State Archives, so I've no clue when/where this marriage actually took place.
There is no little Lydie or Elizabeth or similar in the 1860 home of the Thomas Jackson/Elizabeth in Wisconson, but at roughly 13ish Elizabeth could be living outside the home as a housemaid or similar type situation. And then comes the marriage record in Dunn Co Wisconson for Elizabeth Edwards to Edward Simons in 1867. Then as you know Edward and Elizabeth Simons appear on the 1870 Red Cedar, Dunn Co WI census (the index gives 'Smion') and have first child, Frank, age 2, with them.
I looked in Minnesota for a marriage record for Arthur Spohn and did not find one online, but 1910 Los Angeles Co CA census states his wife Augusta (age 32) was born in Minnesota and the Spohn family appears on the 1905 Minnesota state census.
Arthur Spohn has WW1 required registration. it gives his birth as 31 March 1877 and his full name as Arthur John Spohn.
There is also a photo on find-a-grave for Elizabeth Spohn's grave in Sunnyside Cemetery in Long Beach, Los Angeles Co CA
link to photo:http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GSln=sp...
While I can not view death record, as someone somewhere on here already told you, John W Spohn died in St Louis County Minnesota in 1907. J W Spohn does have a death record there and on 14 Nov 1907 Elizabeth A L Spohn did file from Minnesota as widow. Her application was accepted (as she has both a application and a cert #)...you could order these pension records through the National Archives if you get to that point of search desire. The pension application for her as widow likely gives 'proof' of marriage place/date.
I've enjoyed watching your search, I wish you the very best. I've no doubt you're 'get there', the one thing I've noticed is Elizabeth Edwards Simons Spohn has consistently used for Elizabeth A L when legal records comes to play (from her marriage to Simons to her widow application for Spohn's CW pension to the usage of the 'A' on her tombstone).