[Admin]

//  attempt at auto-surround post with tags
      if ($bbuserinfo[5] != " ") && ($bbuserinfo[6] != " ")  {
        $message = "$bbuserinfo[5].$message.$bbuserinfo[6]";
        }

needs to be:

//  attempt at auto-surround post with tags
      if ($bbuserinfo[field5] != " " && $bbuserinfo[field6] != " ")  {
        $message = $bbuserinfo[field5].$message.$bbuserinfo[field6];
        }

I added field before 5 and 6, and also removed the parenthesis from around &&.

But it's not done yet, you're using $bbuserinfo info, so the header and footer for the posts will be by the VIEWING user, not the POSTING user.
You need to use $post or something like that.