You are right about the 6 months rule. I am not sure about cancelling it and then reschedule. Because you can reschedule a test but once you cancel it, it's cancelled. You might have to pay again. I suggest calling ADA and find out. I had a similar situation. I asked them what the purpose of paying a $100 cancellation fee is if I can just not show up and save $100. ADA told me to save my $100 and not show up. However, since my 6 months was up. I had to pay for the test again. And how would schools know you were a no show. They are probably expecting the score if you put in your AADSAS that you were going to take it in October though. But again, they only care about the score that gets printed.
Don't take the test if you are not fully ready. You'll have to wait 3 months if you take it and dont do as well. But then again, the test may not be that bad. I retook it last week and improved from a 13 QR to 18 and 14 PAT to 21, 19 RC to 25 as well. Just move on when you dont know the answer and practice timing timing and timing.
I like to know which schools average DAT scores too. It's like Big Foot, I heard there are some but no one ever names them!