Tango49,
Sorry to hear you're having a nightmare with your IR.
It sounds to me like you should take a break from training for a couple of weeks, settle your mind and reassess what's going wrong. I would seriously think about speaking with the CFI about your instructor, ranting at students during any stage of flight training is a bad thing. You may even want to think about changing to another flight school!
As for tips, I recommend that you have all memory items from the check list, speeds and engine/prop settings firmly in your mind so that they become second nature.
Try armchair flying. Sit in a chair and run through a complete flight. Call out speeds, engine/prop settings etc - talk your way through the whole flight. Move your hands as if you’re operating the gear, flaps etc. Make RT calls. Do everything as if you're in the aircraft.
Get permission to go and sit in the aircraft with another student and give each other scenarios like an engine failure. Become completely familiar with the cockpit, you don't want to be looking for a flap switch while you're trying to fly an approach!
Ask your flight school if you can use the sim after hours or when it’s free during the day so you can practice your scan and drills.
And this I think is a big one for you. When you're on your flight test, try to imagine that the examiner is just a normal passenger who's asked you to fly them from A to B. Try and relax and concentrate on the job in-hand. You will make a mistake on you flight test, it's very rare that someone will get through a flight test without making some sort of mistake. Don't dwell on a mistake, just put it behind you and continue with the flight - you may do well enough in the overall test to pass!
Good luck, I hope it all works out well for you in the end.