I am definitely sure, the current placement of share button is kind of hidden. I mean it is hidden beneath the "post like" button. Can u place this to the left of the "post like" button or right of it. Just a share button, when a person clicks on it the drop down menu comes with various social medias to share into.
It will be really hard for first time users to find out the share button. I know this can be changed in a custom theme, but even by default the share button should be visible to the members browsing a post.