Finding table name referfences in SSIS packages
If you check the table [SSISDB].[catalog].[packages], you'll find the packages XML. From there, you can parse the XML (might be quite painful) and extract the  tag.

This might be a good start: https://social.msdn.microsoft.com/Forums/sqlserver/en-US/6c31e43f-4f25-476c-8cfa-87f91fbf609e/help-navigating-xml-file-with-sql-nodes-method-against-a-column-of-xml-type?forum=sqlxml