As always, first eliminate any physical reason for the behavior, especially the bucking/rearing undersaddle. That could be a lot of things outside sheer spoiling, including sore muscles, misalignment, saddle fit issues, bit/bridle fit/adjustment/appropriate-ness, teeth, etc. Tread carefully with the bucking and rearing. Those are dangerous behaviors, and even more so when they become habitual.
What exactly do you feed him? If he truly has that much energy, all he needs is good quality graze and grass hay free choice, with clean water and perhaps a mineral supplement.
On the training front, you must be absolutely consistent. With a horse that has been spoiled and treated like a puppy rather than a horse, sometimes some tough love is needed. I'm all for lovin's, treats, and all of that, but there have to be basic ground rules and patterns of respect in place, first. Every interaction teaches the horse something - every formal "lesson" on manners has to be backed up and enforced in the stable, in the pasture, while grooming, etc. Absolutely go back to the beginning and start with some basic lessons on "personal space" and moving his feet at your direction. Sometimes these guys with well established undesirable habits need excellent timing and feel to work out the "right answer." Going with a boxed training system or method is great and can get you pointed in the right direction, but without the consistence, timing, and feel to be totally effective your horse will have a hard time understanding. If that is the case, do look into finding someone with the feel and timing to help you get the ball rolling the right direction.