ubercart checkout review button position
your better off targeting the checkout button via CSS than mess with ubercarts tables on checkout as the $form contains all of the other code which you would need to parse to extract the button and apply it somewhere else.

Just do a position: absolute on the button.

If your CSS isn't up to par, then I would parse the $form variable and preg_replace() it out. You'll need to have good regex skills to grab it.