I have a mare who will do the same thing in any kind of curb bit...probably due to someone with heavy hands, as well...
When I got her, she was buck and bolt type; I couldn't even put my arm over her and she would buck and bolt...so she needed more retraining than just to the bit.
I put her in a french link full cheek snaffle. I also used a rope halter, and taught her to respond to lateral pressure on that as well. I have no issues controlling her in a D-ring snaffle, now. I have tried a mild curb, but she was definitely not ready for it...so back to the D-ring.
So my advice? Find a nice snaffle, and use it...teach him to respond to lateral (side to side) pressure, teach him whoa (try to teach him via your voice, more so than the bit right away, and get a good reverse on him...teach him this on the ground, first...via ground driving. At the same time, start teaching him a specific 'cue' to walk, trot, and canter. I use "walk on" for walk, a "cluck, or click" for trot, and a "kiss" for canter...teach that on a lunge line. When he's got those down, start 'reteaching' the same ones undersaddle, in a safe area...round pen, or an arena. I think if you do your homework, and not 'rush' to get out of the round pen or arena, you will soon have a horse who will respond no matter where he's at. That is what I did with my mare, and we both enjoy the trails, now, because I didn't rush to get out there.
A heavier, or harsher bit will not get the long term results you are looking for, as you have figured out already; go back to the basics, and he will be better for it in the long run.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."