Lee, If this were my horse, the first thing I'd do before attempting to go any further with his training is to have the vet and equine DENTIST come and thoroughly examine him. Particularly the dentist, because this horse is at the age when serious dental issues often arise. The most common issue faced by horses of this age is impacted wolf teeth in the lower jaw, right next to where the bit rests. Wolf teeth in horses are like wisdom teeth in people- they are vestigial teeth from an earlier period in the horse's evolution, and they often come in crooked. In some horses, they never erupt above the gum line at all, but remain buried under it, just below the surface. If something like a bit HITS these teeth, it can cause the horse severe PAIN, resulting in head tossing and evasive behaviors like the kind you have seen with your horse.
All young horses between 2 and 5 years of age should be examined and checked for wolf teeth prior to any training under saddle or in harness. If wolf teeth are found, they should be removed to prevent the horse from experiencing severe pain during training.