Copy 1 site from Wordpress multisite to regular wordpress single site + Fix mySQL so it will not load my CPU

Two parts: 1. Take one site from my wordpress multisite and migrate its articles/categories/images/pages to fresh wordpress single installation (on fresh Cpanel on same server). Both these sites are on same dedicated server (different Cpanels), so copy files can be made with SSH, or i can my hosting company to do it. Some info, this site has 373,000 posts and its DB is 1-2GB, but as i said you do not need to download and upload it. Part of the progress is to change links in DB because there links in wordpress into multisite are little different than in single site. - this cannot be done with plugins because DB is too big. 2. I do not know if it is because o 373,000 posts (add i add 1000 posts a day) or because the DB is 1-2GB, mySQL load my CPU too much (most of the time), i need it to be fixed. Plugins or CDN will not help, if you do not know MYSQL/PHP do not bid !!