My suggestions would be to stop lunging him for the time being and to stop driving him away if and when he isn't doing what you ask. He obviously likes you a great deal and wants a bond he cannot get with his current owner because of her fear of him, and he is sensing you can fill that need, and that maybe you want that too, so maybe that is the cause of what you described are temper tantrums. Why not let him bond with you as part of your working with him? Without some trust and bonding, in my own opinion it is training which is basically mechanical and lifeless.
Arabs are exquisitely sensitive and generally super quick thinkers, and I have found that they respond beautifully when you are intensely dialed into them with your body language, eyes, intentions and matching intensity. They also love that extra praise (big confidence builder!) and are very sensitive to punishment, and need hardly a scolding, usually even a stern no upsets them a great deal. They are great horses to help a person finely hone their intuitive, empathic and instinctive abilities. They are not "difficult," as many believe.
Attachment and trust issues seem to go hand in hand. It's unfortunate that his owner is afraid of him.
As for driving him away when he isn't doing what you ask, I would take a different approach and ask if how you are asking is a factor in his response or lack thereof. If you don't believe that is the case, a milder response to his not wanting to go over a pole, for instance, might be to go back to something he did successfully, praise him like nobody's business (make a real fuss over him LOL) and then ask him again to do what he previously didn't want to do before. The more praise you heap on an Arab sometimes, the more they delight in pleasing you. Building confidence with positive reinforcement, basically. Building his confidence generates his trust in you, and of course attachment is pretty much based on trust, so you two may as well get attached ;)
I hope this helps.