Get Facebook Custom Shares From Page

I have a Facebook app and the ability to use the Facebook or FQL API with valid access tokens for each of my users. The permission includes read_stream.

My goal is to find a custom timeline for the content they have used on specific Facebook pages. This is for the game: users will be rewarded with points for sharing page content. This means that if they click the "Share" button on all pages published on the page: links, albums, photos and status updates, they also post them on the wall.

Requesting promotions directly from the page only provides a general score and not information about users who have shared that content.
/ [page_id] / posts? = Stock fields

Using FQL to query the custom flow for posts with set_id set to the page id gives me multiple stocks (among other things, it skips stocks with photos and shared shares) - and no identifying information on the original page (all of those id's are either user, or null)
SELECT post_id, parent_post_id, source_id, target_id, message FROM stream WHERE source_id = me () AND after_id = [page_id]

Using the Graph API to query user posts also contains no data in the original page, so there is no way to determine the shared_story source. story_tags sometimes contain the id of the original page. Object_id is also sometimes set to the id of the original message, but again not always.
/ me / messages

Is there something I am missing, or another approach that I could take? It seems to me that there are some missing functionality in the Facebook API as generic posts are of a unique type, but most of them do not have identification information from the original content. The link should be there because on the Facebook interface it links directly to the source.

thank