Domain access issue w.r.t viewing a content other than admin user
My answer is based on experience with D6 version of the module but I believe the core is still relevant. As the site administrator (user id 1) you can view all site content unless you disable that option in the domain settings page (Administer >> Site Building >> Domain >> Domain Settings >> Domain module behaviors fieldset >> Enforce rules on administrators:).

With relation to content viewing for other users, it is the default behavior to return HTTP 403 (Not authorized) when a content created specific to one domain without being shared to all affiliates is viewed from a different domain. The option to publish node to one or few of the sites is available in the node creation or edit form. 

If you wish to change the default behavior of specific node types, the option to either allow specific node types to be published to all affiliates can be found in Node settings under Domain. When nodes are saved that way domain access table has an entry for such nodes with affiliated domains as domain_site.