Not really sure, you can in theory install drivers for anything, but that doesn't mean the device will actually work and it will be found. If you have a "pci device" and "multimedia audio device" then you are passing both the gpu and the audio controller on it, that should be fine.
What are you using to hold the gpu from being loaded on linux? vfio, pci-stub? What kernel version is your debian on? You do passthrough both your graphics controller and audio controller on it right?
On Nvidia there was this extra step for spoofing some id, because otherwise the card detects that it is being loaded in a VM and doesn't load. I'm not sure how this works, because I have an AMD card and I don't have to do this.
errorcode 43 was device no longer recognized/not found iirc
Try installing synergy as a server on Windows with linux being a client of that server, I'm not sure where I read that, but it's supposedly the better setup as well, if it also solves your graphics problem good then!