Wow, thank you so much for the extensive response!
Okay, after hours and hours of trial and error, the main problem is fixed.
For some reason, this worked:
-Reverted back to my win8 backup
-Went into safe boot as soon as I could
-Disabled the AMD driver
-Uninstalled the AMD driver
-Windows automatically reïnstalled the original driver
Since then I haven't had the Thread Stuck In Device Driver BSOD anymore.
However, the problem isn't solved yet.
I am currently getting errors on both my AMD and Intel integrated graphics drivers.
AMD: error 43 (Windows has stopped this device because it has reported problems)
Intel: error 31 (This device is not working properly because Windows cannot load the drivers required for this device)
When I try to update my GPU driver (only way to do so it using AMD installers- I can't download specific drivers ]:< ), it installs the wrong drivers because the ID of my HD Radeon 8850M is appearently the same as the R9 M270x. I tried all different installers (AMD Catalyst for win8, AMD radeon minimal installer for win8.1 and AMD radeon full installer for win8.1). Every installer installed different drivers. Some just listed my driver as 'R9 M200 series', some listed it specifically as the R9 M270x.
Main point is that if I updated to one of those drivers, and then tried to access the grahics settings, I would get a BSOD with error code 0xa0000001. I couldn't revert back to the original driver through device manager, because the driver file was gone (it was listed but when I tried to install it it told me it's just gone, wth windows).
Luckily, Samsung Recovery also had a backup of the original system drivers. Through that, I have now access to 2 HD8800 series drivers (2012 and 2014). However, these still give me the driver error 43.
Long story short: Pc works again, but the GPU doesn't. Furthermore the Intel graphics also have some issue.
Any ideas on how to get my GPU working again? (I don't care much about fixing the intel graphics if I can fix the GPU).
WhoCrashed & SysNative reports:
I couldnt run FurMark: "FurMark requires an OpenGL 2.0 compliant graphics controller. Startup failed.". I guess since my GPU is turned of totally it's not possible to run the test haha. So I decided not to try any other tests because they won't work anyways.