Displaying individual fields in a template
You can not print out content fields directly in the page template. content is available in the node template, not in the page template.

The correct way to print out parts of the node elswhere in the page template is to define a block that does that, for example with the ctools module and a specific view mode that just contains the fields you want.

Alternatively, you can load the node yourself in theme_preprocess_page() and then view/prepare them manually and put it in $variables. But using blocks and regions is the standard and recommended way to put something in the page template.