For this one, I first went to the site that OP used to verify the marriage certificate. Once I had the date, location, names, and ages, I Googled census records from the 1930s and 1940s by including all the information I had in the search. After that, I figured John E Evans may have served in the war, so I Googled for service records and verified from a few sources, one being ancestry.com (no membership needed this time). Then I searched for his gravesite, but I still needed his age at death. I found several candidates on ancestry, but only one perfectly matched his family's names from the census records.

The trick is to stay completely objective. I don't care what I find when I start because I don't want to influence the outcome. Many people fall into this habit and before you know it, we're all related to some famous king or queen lol. Just follow the evidence and go with whichever path is most likely and rational.