I think your best and also most affordable option would be to downgrade to our $18/mo plan, which is the cheapest plan that supports Remotely Hosted Downloads -- please see this help page section for further explanation and instructions:
Then you would simply upload your files to any external Web server (such as your Web site hosting server, or a file hosting service like Amazon S3) and configure each product with a Remote Product File URL, rather than uploading the files to us. Files you store remotely do not count against your upload limit at our end, and the unique link we issue to each buyer would cloak your remote URL, minimize file-transfer bandwidth usage and costs for us both, and enforce your link expiration settings. This help page provides some tips for determining the correct remote file URL to use:
It appears you have already upgraded to a much larger plan, but you have not yet paid us the higher price for that plan because your next payment is not due to be sent until the 5th of next month, so you can just downgrade to the $18/mo plan before the 5th without overpaying us.