Views Module "Page" and Contextual Filters
You are close. Remove the "Global: Null" contextual filter and configure your "content: nid" contextual filter this way:

WHEN THE FILTER VALUE IS NOT IN THE URL => Display all results for the specified field
WHEN THE FILTER VALUE IS IN THE URL OR A DEFAULT IS PROVIDED => Specify validation criteria, content, type: press releases

To get the press release links changed, you need to:
- add field "content: nid", exclude from display, and rearrange on top, above title
- edit title and remove "Link this field to the original piece of content". In "Rewrite results" check "Output this field as a link" and enter "press-releases/[nid]".