Hi
I would be able to create an import script, that will take care of importing the feed into site as product. It require direct import and cannot be done with addons as we used to.
But, I think you have choosen wrong platform for a huge site. Wordpress/Woocommerce cannot handle such big data. You should have either gone to magento or other carts such as big commerce, oscommerce or zencart.
Still if you want the script to be development, would be able to help.
Please advise to proceed.
Thanks
Balaji