Take a look at Managing documents using REST.
Make sure that service is enabled for documents (setting->integration->REST).
Path should be
/content/site/<site name>/<culture>/document/<alias path> in you case
http://localhost/rest/content/currentsite/en-us/document/<Your Document Alias Path>
This will give access to you document properties (i.e. properties that defined in page type, including SKU if available). You can copy alias path from general tab.
To access web parts you have to use objects instead of pages i.e. you need to access page template:
PageTemplateWebParts will contain xml with webparts