I would change bits, some horses have a hard mouth and need the heavy duty stuff. I would STRONGLY suggest every time he acts up to get off, lunge, get back on, and if he keeps acting up, lunge again. Just keep doing this until he gets the point to where he will jusy listen or be too tired to contradict. It may take days or weeks, but it will be worth it. If that does not work I would get a trainer.
Always stay humble and kind