The 480 and your CPU are both above minumum. The game can run on that hardware. Minimum specs are a 470 at 1080p on low. So if you're crashing on a 480 on low...then graphics are likely not the core issue.
Now i tried again, BOOM almost same moment of convo game crashes on LOW graphics settings.
^
This is most likely the core issue. Seems like something about your either your save state or installation may be the cause.
0.) Using any mods, or have you ever used any in the past?
1.) Repair/verify the installation through GOG / Steam / etc. Try the quest again.
2.) Reload to a point before that quest was active and try starting it again. See if the crashes occur the same way.
I'd be super-surprised if graphical settings had anything to do with it. Whenever graphics are too much for a GPU, it just chugs and stutters. It doesn't usually result in a crash. If you try to play a game at settings beyond what your GPU/CPU can handle, a game will simply refuse to launch or crash at launch. Normally, games simply grey out any graphical options or detail levels that would not be possible for the hardware.
Crashes are a result of mechanical functions in a game hitting exceptions. Quest instructions, conflict with APIs, driver issues, etc.