As the folks at HSS say, Ess is just not that consumer friendly compared to 2011. Have you thought of using 2011 with a third party backup/restore ( like Macrium ) ? May be easier/cheaper way to go, less admin overhead.
There does seem to be a way to use WD drives with 4K and WHS2. I would read the whole link if you want to go this way.
http://social.technet.microsoft.com/Forums/windowsserver/en-US/889b01be-d333-4fc7-b005-e12b7b236ad7/problem-with-windows-server-backup-2008-r2-with-advanced-format-4k-drive
There is a way to do this, but the drive will have to be GPT not MBR - http://homeservershow.com/forums/index.php?/topic/5136-can-i-use-a-4tb-usb-drive-for-backups/
Another answer, not much different than the above, No, Yes, soon.
None yet, the 64 bit server ARM's are only available through Caldexa, and are definitely not cheap.
Late this year/early next year you will begin to see cheap 64 bit ARM processors aimed at low cost roles like a DIY NAS. No idea...