For number 1, disable debug mode.
For number 2, we can consider making separate permissions for integrations in the future. Historically you always had to have a management-related permission (for forums, threads, etc) in order to make the forumpage-wikipage connection and manage the connection options. Anyone with permission to edit the original wiki page is still able to edit the page's content.
For number 3, we have never had automatic connecting of integration locations to wiki pages. In general, it can cause a mess. The closest we can do without creating a mess is attempting to pre-fill the integration form with a list of similarly-named wiki pages to choose from. Otherwise a separate tool would be needed in the Mass Management Tools.
For number 4, yes it displays an entire wiki page. You can show it collapsed in the integration settings when you connect the content to a wiki page. Check the box "Show an expandable preview of long content."