Dynamic Themes

I am VERY pleased with the dynamic themes. On this page: ads-events-news-featured.php?SI=17&Search=1 you can click on any of the icons EXCEPT Polk Plus and the themed designs work perfectly displaying unique icons, and color schemes for each theme. But then if you click on the polk plus community ads-events-news-featured.php?CU=5&Search=1 and then go back to another SI community the theme does not reset. It appears that is in displaying the listings from the correct SI but NOT the theme. I have attached my template page, the page and the framework page which displays the content. I want to add more CU themes and also want to add convert my entire site to use the themes including my log in page...

1. Can you please help me get the CU theme to display correctly (it does now) and ALSO go back to and display a SI theme.
I have a link to display all that works. (goes back to the default theme - ads-events-news-featured.php?SI=&CU=&Search=1)

2. Can you please advise if there is anything I need to be careful of when converting my log in, insert and update pages. I certainly do not want to break anything.

3. Can you tell me where the session is defined that controls the themes. I see it called with this code: <?php
@session_start();
$defaultTheme= "CHot2012.dwt.php";
if (isset($_GET["SI"])) {
$_SESSION["SI"]= $_GET["SI"];
}
if (isset($_SESSION["SI"]) && $_SESSION["SI"]!="") {
$defaultTheme= "SI_".$_SESSION["SI"].".dwt.php";
$_GET['interestid'] = $_SESSION["SI"];
}
if (isset($_GET["CU"])) {
$_SESSION["CU"]= $_GET["CU"];
}
if (isset($_SESSION["CU"])) {
$defaultTheme= "CU_".$_SESSION["CU"].".dwt.php";
}
if (!file_exists("../Templates/".$defaultTheme)) {
$defaultTheme= "CHot2012.dwt.php";
}
?>

however I don't understand where the sessions are defined. ( I may want to create another)

4. Is is OK to call the above code into the pages with a server side include? I am doing that on the SI-( (dog) template

4. Should the above theme code be included BOTH on the template page and the pages ie ads-events-news.php

Thank You!

5.