Hi, Shauney-
Odds are, you can't "break" the habit of cribbing(also known as windsucking)-unfortunately, it seems to be one of those things that they will NOT ever "give up"-there are theories nowadays about how the activity releases endorphins("feel good" substances, basically).
I have a mini gelding, now 8, who cribs. You CAN buy a weanling/pony-sized anti-cribbing collar made by Weaver, and it does work, though it has to be adjusted very snugly to do so, and you may think that your horse looks uncomfortable(which mine does, but he also eats and drinks completely as he should, grazes, etc.) I have had better results by altering his abode to minimize his opportunities to crib, though this can only work if you have a pen, etc., dedicated only to him-which I have-and I have no board fences, but metal panels, with an anti-climb mesh wire "lining". Truly, I decided not to worry about it-he has never had any medical problems. Sounds as if your colt is in a near-ideal "anti-crib" situation already; perhaps you could try giving him some toys-Jolly ball, a length of thick cotton rope, with no fraying, anything safe he can roll around/pick up and carry/shake, *might*help, simply by giving him something else to occupy his time....Best wishes!