Check Cash on Delivery Availability Using Zip/Postal Code on Product View Page

As you already created a table to store COD available pin codes, get customer's pin-code with below code and match with your table pin -code values.

Mage::getSingleton('checkout/session')->getQuote()->getShippingAddress()->getPostcode();
//or
Mage::getSingleton('checkout/session')->getQuote()->getBillingAddress()->getPostcode();

Now you need to put a condition to show COD method. Update below file...

app\design\frontend\base\default\template\checkout\onepage\payment\methods.phtml

Find code near line 43

if(($_method->getCode() == "cashondelivery") && --Your custom condition--)
     

It seems you want to calculate shipping cost for individual product and not on for whole cart total. In that case you follow below code to calculate shipping cost per product:

<?php
class Yanted_Export_Helper_Shipping extends Mage_Core_Helper_Abstract
{
    public function calculateShippingCosts($productId, $country,$zipcode, $storeId = 1)
    {
        $product = Mage::getModel('catalog/product')->load($productId);
        $item = Mage::getModel('sales/quote_item')->setProduct($product)->setQty(1);
        $store = Mage::getModel('core/store')->load($storeId);

        $request = Mage::getModel('shipping/rate_request')
            ->setAllItems(array($item))
            ->setDestCountryId($country)
            ->setPackageValue($product->getFinalPrice())
            ->setOrigPostcode($zipcode)  
            ->setPackageValueWithDiscount($product->getFinalPrice())
            ->setPackageWeight($product->getWeight())
            ->setPackageQty(1)
            ->setPackagePhysicalValue($product->getFinalPrice())
            ->setFreeMethodWeight(0)
            ->setStoreId($store->getId())
            ->setWebsiteId($store->getWebsiteId())
            ->setFreeShipping(0)
            ->setBaseCurrency($store->getBaseCurrency())
            ->setBaseSubtotalInclTax($product->getFinalPrice());

        $model = Mage::getModel('shipping/shipping')->collectRates($request);
        $costs = array();

        foreach($model->getResult()->getAllRates() as $rate) {
            $costs[$rate->getCarrier()] = array(
                'title' => trim($rate->getCarrierTitle()),
                'price' => $rate->getPrice()
            );
        }

        return $costs;
    }
}

You need to create your action and should make an ajax call to get this rate dynamically.

<?php
$costs = Mage::helper('yanted_export/shipping')->calculateShippingCosts('123', 'US','10007', 2); 

Hope this can resolve your problem.