Define a post’s title and slug from Custom Fields

by

Try replacing 

 $emp_fname = get_post_meta($postarr['ID'], 'emp_first_name', true);
 $emp_lname = get_post_meta($postarr['ID'], 'emp_last_name', true);

with 

$emp_fname = $_POST['emp_first_name'];
$emp_lname = $_POST['emp_last_name'];

Replace the $_POST array keys with whatever the field name is on your form