Wow! Or should I say Super Wow! That's a lot of info. Will look it over and see if I can come up with something for you. It does show right of the bat that Windows is installed in the MBR of /dev/sda. I don't remember asking this before, but does Windows currently boot OK? Just curious. Linux should have no problems dual booting with Windows, so this is indeed puzzling. Thanks for the detailed info, I'll look at it a little closer...
By the way, in all the reading I've done and from personal experience, GPT is the best partitioning scheme IF YOU AREN'T GOING TO DUAL BOOT! Linux will boot to a GPT partition, I've done it, however looking at your logs above, they clearly state that both /dev/sda and /dev/sdb are GPT disks, and not only that, but /dev/sda is housing an EFI boot area in the MBR. This is your whole problem in a nutshell!!!
As stated previously, your hardware is quite obviously UEFI enabled. Debian by default, and therefore VSIDO as well, will not be seen while this EFI partition remains in place. It is the first place your BIOS looks for a bootable OS disk. Unfortunately you are not going to get VSIDO installed while the EFI partition is in place and enabled in BIOS. I know of no way currently to get around this issue. (short of the aforementioned post where I mentioned deleting said partition)
At this point I do not know of a way for you to do what you are trying to do and still be able to run Windows at a later date. There are disk-cloning tools you could use to BU the current state of your drives, however, I'm not 100% certain the EFI partition in the MBR would be saved. So I don't feel confident in telling you to go to the extreme of deleting that partition. As I said before, doing so would surely guarantee that your Windows OS would not install again. This is MY experience with EFI, and someone else may have a way around this. If so, I've not found or read about it anywhere.
Also, before everyone jumps on my back and starts pummeling me, I know that Debian does indeed now have a working EFI installer. VSIDO does not. While I have done it, I believe it to be beyond the scope of these forums for me to tell you to "do it my way"!
Again, your log files tell the story. Both disks are GPT partitioned, and /dev/sda does indeed have an EFI boot partition on it. You will NOT be able to get Grub2 (or SuperGrub) to install to that particular partition.
As an aside, I have a UEFI enabled laptop that came preinstalled with Windows 8. I created the BU DVD's that MS recommends you do since they are to cheap to include install media. I just tried to "restore" my Windows 8 using these DVD's. As I have deleted my EFI partition in order to insure Windows never again graces this particular PC, the restore procedure failed flat and right away. So, with that in mind I would assume your situation to be the same. Delete the partition, and Windows will NOT restore to your machine. I will never use MS products again, so it was with some glee that I deleted that partition off of my laptop!
Ubuntu and Debian (Ubuntu is Debian based) both indeed have UEFI enabled installers. However, these do not include Grub2. They both use what is called 'grub-efi-amd64' (or 32 I assume for 32bit systems) to boot the system utilizing a FAT32 EFI partition just like Windows. The grub-efi-amd64 has a "signing" feature which allows for the EFI boot process as well as even being able to take advantage of the "Secure Boot" feature.