so, your getting the value to use in the search using this code:
$productName = $_GET["Product"];
you could remove ARM from ARMCHAIR using:
$productName = str_replace("ARM","" ,$_GET["Product"]);
and where you want to use includes, you will need to edit this line:
$rsProducts->addFilter("ProductName","=","s",$productName);
to change the filter type "s" (string) to "i" (includes)
$rsProducts->addFilter("ProductName","=","i",$productName);
also edit the SQL, which you don't include here, to change the where clause from = to LIKE