edit the length of the content *you* are outputting from your site? That plugin has been posted before (in fact, I posted it a couple times recently):
location - external_query:
PHP Code:
unset($vbulletin->GPC['fulldesc']);
$vbulletin->options['threadpreview'] = 200;
$hook_query_fields .= ",LEFT(post.pagetext,400) AS message";
Play with the numbers unti you get what you want. It won't be immediate because of the caching, so depending on what you set, you'll have to wait a bit to see results from that.
I've never looked into striping out the bbcode. What I'd do is find another part of the site where this is done and steal the code and create a plugin to add the function to the external.php page.
Also, this site is a volunteer run site. We don't have the answers for everything so you may not get an answer to your question.