I agree, back to basics is always very good and affective for you and your horse. Aslo try maybe learning to ride with no hands, sounds crazy for helping your horse not be strong on the bit but its amazing what you can do riding with no hands shows that alot of ppl depend to much on there reins, just and example me and my horse jumped a 3ft vertical with no hands and his never jumps so under himself and balanced in his life it was increadable! Plus when I rode him with no hands that's when he was able to hold a beautiful frame without me nagging at him to do so!! :P also try punching him and then "catch " him with the bit. Hope this helps :)
Our Hoofbeats were many, but are Hearts beat as One.