I think that trying a bitless bridle/hackamore/side pull would be a good idea. Of course, you only want to do this in a confined area, out on the trail is not a good idea. A twisted wire bit is definitely not something I would use on a green horse! Yes, any bit can be mild in the right hands, but it can also be a weapon. Sounds to me like this "trainer" solved the bucking issue but caused a boatload of more issues. If he didn't do it before, the striking and general disobedience on the lunge is yet another example of how this trainer treated your horse. It's so hard to find a trainer that you can feel comfortable with. I have yet to meet one that I would feel comfortable leaving Jackson with, and I know several rather well. It's going to take time to make up for the bad experience the trainer created for your boy, you'll need a lot of patience, but don't give up. I have found that often the horse you work the hardest with eventually gives you the BEST reward! Unequivocal love and trust.