My horse can get startled or spooked; however, she doesn't take it out on me. I pull on her reins, and she stops dead in her tracks. My horse is a very hot horse. She doesn't make a habit of throwing me off thank goodness.
I hope that you will think about your own safety. This horse is not working out well for your for sure. He is not worth being injured. When you were out of work for weeks due to him injuring you, has the stable owner paid your wages? Did they pay for your medical expenses? You could get killed, then what would your loved ones do? Just some things to think about.