Following the instructions provided by you and launching the modpack without twitch worked after i changed the allocated ram from 2GB to 4GB. The problem is that I'm experiencing some kind of flickering when Minecraft is running now.
Edit: Flickering happens only when minecraft is not fullscreen and it's rendering whether on the start screen or in game. Minimizing the game or pressing esc when playing stops this. Apparently when it renders it messes with my monitor calibration profile, cause is unknown.