You are not going to be able to do it. You can take the ISO and convert it to a IMG file and then use dd to apply the IMG to a USB drive, or think about using rEFI to make a bootable usb and then copy the IMG contents - but in the end, the firmware updater code is expecting to be run from an optical drive on the esata bus and will not work from usb.
your options are:
1 - boot camp and use windows
2 - pull the drive and put it somewhere where the updater can work
3 - make a partition on the spindle drive and look into rEFI on there - you can then boot from there and run whatever.