Hey OP, I saw some of the posts online with people saying they figured it out but with no written solution...After hours of working on my i7559, I figured out a way to install win7 properly.
Here are the steps I took: Create a bootable USB of Win7 with GPT by using Rufus, leave format to default FAT32 Use Intel Windows 7 USB 3.0 to update the install.wim and boot.wim that is on your USB bootable win7
On the Inspiron: Power it on and press F2 for Setup Go to the Advanced Tab then go to Misc Devices, enable USB Debug. Now go to the Boot Tab Leave "Boot List Option" to UEFI Disable "Secure Boot" Go to "File Browser Add Boot Option" Select the usb device you have, then in its directory go to the "efi" folder, then "boot", then "bootx64.efi" It will then ask you to name that Boot option. Change that boot option to be listed as number 1. Restart computer to install Windows7
On another computer, save the Win7 drivers that you can download from the Dell product support page onto a usb. Plug that usb into the i7559 and install all drivers.
Hope that helps!