Hi!
I'd rather give a shout here than with Yoast, since their support isn't easy to deal with.
I would expect the opposite if you pay for the Premium support. It sounds reasonible that it is just impossible to support millions of users for free ;-)
Yes WPSEO does not include custom post types and custom taxonomies titles in Strings translations. But you can do it yourself easily.
Look in WordPress SEO directory. You will find a file wpml-config.xml. Thus you will see how WPSEO makes for posts and pages. Then, inspired by the WSPEO file, create your own wpml-config.xml and put it in wp-content/polylang.
Don't modify the file from WPSEO as your modifications would be lost at first update.