Add options to admin UI for overriding positioning & hide title of Gigya Login Block

I am having trouble getting hook_form_alter() to override the position of the Gigya Login Block element in either user_login or user_login_form. Before we had a stable release, I did this simply by hacking the code. But now that the module is stable, I didn't want to fork the code, so now I am trying to do it in the custom module I use for my site's customizations.

I have reviewed http://www.lullabot.com/articles/modifying-forms-drupal-5-and-6 and I can create a theme function called um_user_login() in my custom theme (called "um"). I made a modification to theme_gigya_login_block, in my theme, so that it wouldn't include the JS code a second time, since I thought that might be causing issues.

It seems like the #prefix element shows up on the page even after I have unset it in my theming function. On the other hand, I don't consistently see it in the $form array, even when I haven't unset it. This is very puzzling, to say the least.

I have given up on trying to theme the form the "right" way now, and am just going to do it in the actual module code. It would be great if azinck or someone else could figure out what I'm doing wrong though, so that I won't have to continue with a forked version of the module.

Below is the code from my template.php:

function um_gigya_login_block($form_id = NULL, $suppress_title = TRUE, $add_js = TRUE) {
   if ($add_js == TRUE) {
    gigya_login_block_js();
    $login_js = 'Drupal.behaviors.gigya_login = function(context){ Drupal.gigya.login(); }';
    drupal_add_js($login_js, 'inline');
  }

  if (!$suppress_title) {
    $title = t('Login using social networks');
    $output = '<h2>'. $title .'</h2>';
  }
  else {
    $output = '';
  }
  
    $output .= '<div class="gigya-login"><div id="'. variable_get('gigya_login_uiconfig_containerID', GIGYA_DEFAULT_LOGINUI_CONTAINERID) .'"></div></div>'; 
			
  return $output;
}

function um_user_login($form) {
	$form['#suffix'] .= '<div class="use-text"> or use </div>' . theme('gigya_login_block', 'user_login', TRUE, FALSE);    
	unset($form['#prefix']);
	$output = '';
	$output .= drupal_render($form);
	return $output;
}