Expert in SEO / webmaster tools / sitemaps / magento / mirasvit SEO extensions

General information for the website: magento e-commerce childrens site with wordpress blog
http://picturemyworld.co.uk
Description of requirements/features: Traffic dropped a month ago (although were only 20 visits per day anyway - now 1-2)
Seach queries reduced at same time
site was previously moving further up google rankings for "Kids murals" but now does not show
62,000 404 errors recorded on Webmaster tools (ongoing)
Wordpress blog sitemap "not found" (warning in panel "Your .htaccess file references your blog route but should reference your WordPress installation directory")

It maybe due to new extensions (Mirasvit SEO), Wordpress Yoast SEO plugin, sitemap configuration, Htaccess file, general settings, other

I'm looking for someone who has excellent knowledge in all of the above and can review everything and configure it properly.
Extra services needed: Domain, Installation, Optimization
Extra notes: