I tweaked your version and now the byline (author and date) elements seem to appear for all articles (there are two different styles of the articles when I view them by clicking on link in the rss feed page and the byline is coded and appears differently in the two formats).
Revised recipe and mobi output attached (two files) Please note for some articles the article picture appears in the middle of the byline in the mobi. Not a big issue as the info is all there.
One of the two article formats has a right-hand sidebar with 'Most Popular' and 'Related Posts' sections. Your version eliminates the text but the photos in those boxes appear in the mobi output and are not for the article itself. I tried to get them out with remove tags but could not. Could those images be eliminated? example of that article format linked below -
http://thefederalist.com/2018/05/04/...f-destruction/
Thanks!