Set unlockFPS 1 . Even if your PC can't reach 60 FPS, uncapping it prevents the game from forcing a drop to 15 FPS when it can't maintain a stable 30.
Remove post-processing:
You must disable in-game Anti-Aliasing and Motion Blur in the game's menu before DSfix will work correctly. Failing to do this can cause a black or flickering screen. 2. Low Graphics Settings for Max FPS dark souls prepare to die edition low graphics mod