How to pass the nid from hook_node_view to the submit function?
You don't need to use form here. Just use l() with the button name and the link path.

function mymodule_node_view($node, $view_mode, $langcode) {

if ($node-&gt;type == 'my_type') {
   $node-&gt;content['redirect_button'] = array(
     '#markup' =&gt; l('Redirect button', 'yourpath/' . $node-&gt;nid);
   );
    }
}