As for the pre-req update, I understand I'll need to install KB3058168 (its pre-req KB2919355 is already installed).
But in my Product Keys section in Relationship Summary, I see a Product for "Windows 10 KMS" as well as the product "Windows Srv 2012R2 DataCtr/Std KMS for Windows 10".
Which should I use? Both are different keys.
My KMS host is a 2012 R2 server. And I have product keys currently for 2012 R2 Std Data, Office 2010 and Office 2013.