If you still own him and haven't given up.
Forget about the "training" he had its no good. And yes the twisted wires are very common bits for Trainers that don't know what they are doing or are after a quick fix[30 days of training that really takes 6 months] Once the mouth gets SORE horses aren't strong[pull on bit] have a good head set[low-western pleasure] Its a bully tactic and no genuine horseman would ever use it as a training method.
Head tossing is very common in young/green Arabians.
If you are confident[its all about attitude] Get a straight bar Rubber snaffle. They are about $5-10. Use a set of draw reins they go from the girth to snaps on the bit rings to your hands. Use these and your regular reins, just ride as normal if you can walk thats a great place to start. He will try to toss his head, but the draw rein will maintain a constant pressure which is what he is trying to avoid. Arabs are super smart and usually only need a few sessions with these. You do need the other reins as you really don't have brakes with just draw reins-they draw the head down and some horses are very content to continue traveling around with their nose on their chest. If he should want to panick, just release the pressure and start over in smaller increments.
The bit, straight bar only applies pressure to the bars[where teeth are]
rubber is soft and flexible to allow swallowing and tongue movement
The ends should be O-ring/full cheek/D-ring any end that doesn't create leverage.
The more quite, easy not really training rides you have the better riding horse he will become. Arabs are tricky- you must always ASK/SUGGEST never TELL them what to do.