When and if he does it again, pull over to the side of the road, switch the engine off and get out of the car. Walk around to the passenger side and just stand there. dont say anything. Your dad will ask whats happening, take a deep breath and say to ya dad that he is stressing you out, and with his behaviour he could cause you to have a accident.
I did this to my dad back when I got my Learners (Australia) and he relaxed on the general driving, but he also taught me how to safely stop/steer a car in emergency situations.
If ya dad is still stressing you out, dont drive with him, tell him that he is unsafe to teach you, use ya mum or PAY SOMEONE TO DO IT PROPERLY!!
Best of luck with the driving