I think you are making it too hard. Download the Rom you want to run to your device. It will be on your virtual sdcard. It will be in the download folder or the download folder for your browser. If you want to download the Rom to your computer, just connect your device via usb to your computer. If you have the right drivers installed your device will show up as an MTP device and you can access it like any other storage and copy the Rom over to your device. Just like you were copying it to a real sdcard.
There should be no need to format your 'card'. If you feel like your device is that whack then just flash back to a stock image and start over from there.
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Swyped from my N7
Current: PA 2.99 b9 & M-Kernel+ a26