All right, I re-installed windows, fixed my fps, it's pretty constant now ~140. GPU is at only ~10% though while in-game, but if i switch my in-game video settings to "very high" , it goes up to 20-30%.
The problem that i still have now is that the game is flickering, it seems like some sort of hz sync problem, but i have no clue how to fix this.
The feeling i get while playing is that of discontinuity, the screen being unstable and it gets worse the longer the game lasts.