If you keep sharing links Post Reach becomes low
Best format for shared picture are huge Formats 600×600 is recommended by stuff . Much better 1000 x 1000 vimeo style HD thumbs . Must not be in the page but at least linked in the og:image Tag.
Only uploaded video works .Youtube and Vimeo external links are handelt like links not video. Tagged User in video by user . Expetion cusom own videoplayer with great video content. Can go viral if community is used for these kind of posts
Very high reach should be at least 500 words to cover feed space and well written. Provoke a answer after read . mostly for higher aged people
Bigg APP Post
Instagram Twitter Forusquere convert minimal to some close friends from the same network. Probably should be limited to FB List who have account at the other platfrom .