How do I display multiple words in primary links menu title on separate lines?

You could modify your page.tpl.php to replace the spaces with <br /> like this (snippet from my page.tpl.php)

      <?php if ($primary_links): ?>
        <div id="primary" class="clear-block">
          <?php foreach ($primary_links as $link): ?>
          <li><?php
            $href = $link['href'] == "<front>" ? base_path() : base_path() . $link['href'];
            print "<a href='" . $href . "'>" . str_replace(' ','<br />',$link['title']) . "</a>";
          ?></li>
          <?php endforeach; ?>
          </ul>
        </div>
      <?php endif; ?>    

Pete.