Hi,
I did a Google search for the Smith-Lyerle Cemetery but didn't find it. You can contact the Union County Historical & Genealogy Society & Museum,
www.unioncountyilmuseum.com/ and hopefully they will have info about it. They also might be interested in your info because these family cemeteries sometimes go unnoticed.
Sounds like John Jackson Smith and Massey Jane May married and then divorced. Early divorce records are in general court records and later divorce records are on file at the local court house or Illinois Archives. The Illinois Regional Archives Depositories,
www.cyberdriveillinois.com/departments/archives/IRAD/irad.pd... will make copies of documents.
I can't investigate your #3 question without knowing John Jackson Smith's birth date and where he was born and where he last lived. The Genealogical Society might be able to help you with that too. Successful Searching!