Don't worry! it's just a small matter during your life long parental job. You still have a long way to go. This is just a little start. Stop thinking of it cause your worry will not do any help on the result.
I suggest you consider you will fail and if you made it that's a bonus. Then you will be happier.
There is not a rule than only by attended this school's N1 will your baby succeed in future.
Relax a bit. At this point of time you can't control. I also assume fail. 3000 applicants but accept 80 N1 wow..too difficult....so many people want to get in HKPS...and the birth rate reached it's top in past 10 years...no way...
Besides the kid has to be smart, also needs to be lucky enough I believe.
So hope for the best, prepare for the worst. The back up I picked for my son actually is also good school. I am sure the same to you for your kid.