That's so great! Have you thought about doing Natural Horsemanship or anything? My pony responded really great to that.
I think with the whole brakes thing though, I'd really think about what I want from him. Different bits serve different purposes and have multiple effects, not just brakes. A dutch gag bit for example has different rein options which makes it versatile to use one bit for a variety of situations, depending on how much control is required. The of this bit creates lift upwards in the mouth and a varying degree of leverage depending on the rein setting used but it's not advised for a horse that puts it's head up because of the raising action it has. There are so many bits, standard ones, Neue Schule, Myler, Bomber bits, you really need to do some research and find a bit that works for you both. Do you have a bit hire company near you?
I used to know a pony that would take off in a field no matter what bit it had in. It didn't care and nothing worked. She tried everything from dutch gag to pelham to different nosebands to different mouth pieces. Nothing worked. I often think if a horse or pony wants to go, you can't always stop that with bits and nosebands. She ended up just accepting the pony for what it was and dealing with it as best she can but I'm not suggesting you do that, just saying a bit might not be the answer. But then again it might.