Hi,
Well it is good that he isn't a burned out school horse!! For being stuborn all i can really recommend is working on suppling him, suppling mean flexing him giving to the bit you relaxing on him. IT will keep him focused and help him relax. I had a stuborn horse he was really hard to ride and feel good about riding him. But after Many lessons and horses just bonding with him he relaxed and soon our rides were made Very nice!!
When you try to move him forwards use your seat and a soft squeeze, soon he will be responding so nicely to you. It all really takes time.