And So I produced a action add_action( 'header', 'admin_bar', 8 );, to ensure that it loads within the header. However, I'm not going it to strain on certain pages, for instance, post-new.php. Can I've got a condition for hooks to load only certain pages?

In my opinion there's a $pagenow global. unsure whether it's there however, you could var_dump($pagenow) around the pages you need to exclude to obtain the value then make a move such as this inside your function...

function admin_bar() {
  global $pagenow;
  if ( 'post-new' != $pagenow || 'dashboard' != $pagenow ) {
   //execute code
  }
}