yeh the studying and forgetting is very common. Honestly, I couldn't even get any sleep the night before the test. I just layed in bed for 8 hours tossing and turning, never feel asleep cause in the back of my head I "knew" I wasn't prepared enough.
In my opinion, You study all your DAT material, you cover everything front to back 1-3 times. Once you do this for ALL the material, then your ready to take the exam.
As for the QR section, IMO the best study tool out there is math destroyer (not DAT destroyer), this book has 10 QR tests, total of 400 questions, if you master them, you should be in good shape for the test cause most of those problems are going to just reappear on the DAT with different numbers.