Structured data incorrect for Blogposts

Every blog post on Independent Publisher generates a bunch of structured data errors (checked via https://search.google.com/structured-data/testing-tool).
The theme is embedding an itemprop of type blogPost for the main body of the post inside an overall itemprop of type WebPage for the whole page – this is an error. It then has a property of mainContentOfPage which isn’t recognised by google, and it then omits the mandatory properties of author, headline, image and publisher.

All in all, the structured data is a bit of a mess for blog posts.