can understand your frustration, I´ve been on vacation only for one week and started dreaming of being in the rift after day 4 or something. Cant really help you with SP1 install bug bur regarding the 10 upgrade, I think it simply comes down to if you need to use your PC for productive work or just gaming pleasure. I don´t loose any money by having to reinstall my PC so I took the chance. Just copied my reply from the Win 10 thread:
I have quite a collection of usb peripherals plugged into my Workstation all the time and its business as usual after the update. (I was prepared to fight with drivers and curse Microsoft, like it should be with a major windows release! ;-)
Even strange ones as my Nikon Coolscan V (35mm Film Scanner) wich was last supported on XP and was a huge pain to get running on Windows 7 and my Dualshock 4 Controller via Bluetooth/DS4Windows work. (those two were the only ones with no driver support for Win7/8 and my workarounds keep working, very nice!)
other gaming/work stuff I allready tried and can confirm working under Win 10: Defender Cobra M5 Joystick, CH Pro Throttle, Logitech DFGT wheel, Roccat Tyon, Samson Go mic, Huey Color Profiler, Audioquest Dragonfly and iFi Mini Audio Dacs.. Fanatec CSR+CSP
I like most things in Windows 10 but DK2 is another level compared to 7 in my opinion (DX12 or WDDM2 I dont know why). I used 5.0.1 for a few weeks since its working as usual in win7 (no Direct mode sadly) but after trying 0.7 with PCars and Dirt Rally I tried 6.0.1 again for Elite and AC and decided the little pain it brings is so worth it for those two games. I keep switching runtimes between games now but mostly play E

and AC.
Hope you can solve your problem and enjoy E

soon! QCQ is pretty addictive to ;-)