Block above content should be simple however
There is a number of Block related access modules that can help you: 

Block Access allows you to set individual Block permissions. So after you create those Blocks, allow the specific user Role to edit only those particular blocks above Login and other pages. 

You might also create a special Region within your theme just for this purpose, and set permissions for that Region blocks with Block Region Permissions. 

You can set finer control over the Admin Block pages with Block Content Permissions.