At this point hearing that the Dark Souls PC port is terrible is no ground breaking news. Many people, including myself have been struggling with the poor optimization and customization that this port has plagued players with. Here is a mod that will help fix the frame rate and resolution cap for the PC version, as well as a few other mods to help the game look a little better.
Various visual improvements to the game.
FPS cap and res cap Fix.
Blighttown high res texture pack.