Hi, Replacing www.domain.com/wp-content/ with wp-content.domain.com/ in database was actually point 4 in the keycdn tutorial 
This is not topic of Virtualmin, but anyway, you need to add cors header. I did not even notice because i dont use woocommerce but one of my plugins css was also not loaded because of missing cors. You just have to addcors header. If you use apache then add next lines to your public_html/.htaccess (found the solution here: https://stackoverflow.com/questions/41036415/cors-with-php-wordpress):
AddType application/vnd.ms-fontobject .eot
AddType application/x-font-ttf .ttf
AddType application/x-font-opentype .otf
AddType application/font-woff .woff
<FilesMatch “.(eot|ttf|otf|woff)”>
Header set Access-Control-Allow-Origin “*”
Solved in my site, hope it works in your site as well.