I too am sitting GCSEs this year and my advice to you is CHILL OUT. Over stressing is possibly the worst thing to do right now. At the end of the day, you only have 3 days left and you can only do so much! If you are capable of 7s anyway you’ll be absolutely fine and I’m not sure I agree with your fathers tactics- no offence. Do this for you, this is not the end of the world, think of it like this- on exam results day it’ll all be over! See that as a reward but for now relax your brain and try not to cram.