well, sounds like you got a true QH! Lol yes all the things you said are good. Like the first comment- carrying a crop you may not need it but often it helps. You can also try spurs if you are expieranced and can use them as a training aid, not relying on them because your horse may get unresponsive to them if they are relied on instead of used to train. You may also try another bit? But it is generally as simple as you must be a very active and engaging rider. I am not sure what you do with him, but there are some different things I have done to get a horses motor goin... like I had one horse we would go around and walk and bend and sidepass and legyield and then I would take my right hand and start at his poll with my thumb on one side of his crest and my fingers on the other and press down hard and rub all the way down his neck and scratch his upper neck and then go and trot and bend lots and get him really moving and working and he would really move forward then. He was a jumper. Natalie, an 18yo reining mare, can have her rater dead days.... but if I want to get her awake and ready to do something I just run her down the center once or twice, she gets so excited about the prospect of REALLY doing REINING and stopping etc that she immieaditly is ready to go up and move forward when I ask her to. Another thing is taking a horse out and cantering it in a field.... the down side to some of these things with some horses is that some horses will get wound up and will stay wound up, then you have the opposite problem.
However, one of the best easiest things I would suggest to try first is to ride him somewhere else. I know our hunter horses would get this way or sour... because all they did was the same thing- go in the arena- walk trot canter- change directions and repeat- etc. one of the best things I think you can do for your horses mind regarding to riding is to change things up, change location. Go left first instead of right. Take a lesson in a different ring or go on a trail or ride in a field... just the change of scenery often brings them back a little bit fresher and willing to work. It is simple but it has worked for me a lot and is included with my above methods!
Also, you could try and feed him some oats or alfalfa... both have tons of energy, so much I knew one half arab that would get high if he got too many oats.... I have never tried an energy supplement because I have never needed to use one, more needed calming than anything! Haha, but it may be worth a try. Maybe smartpack has something that will get his energy level up?
Hope it helps!