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The big difference, as far as SEO is concerned, for a subdomain blog (blog.) versus a directory (/blog) is how the link credit is attributed. Search engines see a subdomain as a completely separate site. Any backlinks you get to your blog content will only benefit your subdomain blog. When the blog is a directory it is an extension of your main domain. When you have it set up that way and build content the backlinks received for the content can help build the domain authority. I personally prefer to setup blogs as /blog and would recommend that method although I have also seen people successfully have subdomain blog setups as well.

If you click on "Admin" in the top right, then under "View" click on "Scheduled Emails" you will see the scheduled emails for that profile. On the far right you will see "Actions". Under the actions button is the option to delete.

I actually show both terms graded as a C for that page. If you run the page grader again (http://pro.moz.com/tools/on-page-keyword-optimization/new) it actually lists out exactly what items it looks for and doesn't find and those are the reasons why the grade would be lower. If there is a green check mark to the left of the item then that means it was able to find this on your page, if the green check is missing then that is something you should focus on.

Yeah, I would 301 redirect all of the old blog articles to the new blog articles.