I know it's frustrating, we have come across lots of listings like this in the past. About the only thing you can do is flag the listing and explain that it's a duplicate listing. You might have several people using different Google accounts flag the listing, as well.

Generally speaking, if you think of the keyword set as part of a large "topic", then you should optimize your site's home page for the main topic in general--and then the sub-topic keyword(s) and the "sub-sub" topic keywords would also be pages, as well. The sub-topic keyword would be linked from the site's home page, and then the sub-sub topic would linked from the sub-topic's page.

I like to think of this as a theme pyramid approach

Main Topic
     Category
          Sub-Topic
     Category
          Sub-Topic

What I believe you're seeing is information taken from the knowledge graph. Wikipedia is a data source of the knowledge graph (there are a lot of sources), so it's logical that Google would include that information in their results.

The 404 errors and other crawl data is provided by a separate database in Google, so the timing of the links and the data you're seeing isn't exactly "in sync" so to speak. I would do a few things--look at the pages to see if there's something on your site that might be causing the errors.

Another option is to look at the link data to see if there are any links pointing to those pages. I would use another source, such as OSE or Majestic.com to see if there are links pointing to those pages that Google isn't reporting (which is often the case).

Whenever you deal with links, even though I really like OSE, typically we have to compile all of the link data from multiple sources. We typically use OSE, Majestic, ahrefs, Google Search Console, as well as others and compile all of the links into one spreadsheet and then look at them there. Different sites have different crawlers and no one source is the most accurate.

Federico is right, it's not necessarily how often you post, but what you post. Keep in mind, though, that typically just posting is not enough: make sure that you do some extra promotion of each post, like adding it to your Twitter account, Facebook account, Google Plus account, etc. so that there are links and social media mentions going to each post.