Uh-uh. Keep your keywords at a minimum. Don't overly repeat the same keys in one content. What you can do to add weight on your primary keyword is to include or mix in related keywords. This way, you won't appear too obvious to Google. Obvious means over optimizing.
Your keyword strategy should have given you some idea what you want to write about. For blog posts, you will usually aim for a long tail keyword (containing multiple words).
It is possible but it is not advisable. It will give a negative impact to your site.
Search engines will look at it as if you are trying to manipulate them, which is basically the idea of using the keyword multiple times.