Hi @savvaskef
To answer your last question last, why are you creating a front end form? Why not just add in the WP edit button, which will link the author through to the backend?
http://codex.wordpress.org/Function_Reference/edit_post_link
Or perhaps you could use the live_edit plugin?
http://wordpress.org/plugins/live-edit/
Let me know if either of these are possibilities. Thanks
