I really don't know how to explain it, but in game, everything seems to jump, almost like there is a delay then BAM, split-second movement. Is anyone else experiencing this? Can it be fixed?

If you do want to keep your dual core optimizer (for other applications, for example) then just try running this game with only a single core being used. Start it up, ALT-TAB, bring up the Task Manager, find the XIII process, right-click it and set core affinity to just your first core (core 0), then go back to the game. That might also work without you needing to remove your optimizer.