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I had a site a while back with the same issue.  What I did was take the posts from the smaller site and re-posed them using same post date on the bigger site.  Then I added a rel="canonical" for each of the old domain (smaller traffic site) posts to the new bigger site.  I let the blog sit for a few months and then redirected the entire domain.

I've had these same issues.  A lot of this can be solved with the Yoast WordPress SEO plug-in.  Adjust your indexation settings and eliminate a lot of duplicate content.

From everything I see in your code the rich snippets are being used very effectively.  This should only help your results and will not hurt them.  If Google makes an announcement and suggests that websites and especially product site use rich snippets then you can expect that they are going to use them more and they will only help your organic results.

The only suggestion I may make is that you may have wanted to use the schema.org format.  This is the format that Google recommended publicly.

This same issue has baffled me many times.  The main suggestion that I have is to get some reviews.

You may also want to make sure that the address in places matches exactly the address on the website and any other websites the business is listed on.  If possible get the address on their website in hCard format.

Try the Yoast SEO plugin.  This will allow you to put nofollow and indexation rules that will help with blocking the crawlers from indexing archives, admin pages, comments, tag pages, search results and more.  This will really clean up your errors and make the site more relevant to Google.