I need help with the headings / headers in my blog posts.

RankIQ's reports do not give guidance on writing headers. 

The best practice is to craft your headers based on the actual content of your blog post. If you write about your keyword phrase in a particular section of your blog post, it may be appropriate to use your keyword phrase in that section’s header. If it makes more sense to use the keyword phrase in the text and not in the header, then do so.

Always remember that you should be trying to write the highest-quality post for your keyword, and avoid keyword "stuffing,” or you will be penalized by Google (very bad).

The best practice is to reach an A++ grade for each article, and also meet or exceed the word count.