Change the priority weight for the sitemap of About, Archive, and Colophon to 0.5.
Add an option to exclude pages from the sitemap.xml in YAML front matter, with out first exclusions being 404.html and index.html (as it’s already included).
Add logic to exclude XML feeds, pages without layouts, and/or pages that are excluded specifically with the added exclude: yes in the YAML Frontmatter to sitemap.xml.
Add fb:admins meta tag to header.html.