A way to know you can stop revising this subject.

Well long story short(OK it is still long), I have been studying, found my exams to turn out great this far now i have a little more period to study and lots of other exams are coming up but i really do not know how i can finish with a subject. I have no way to know that i am done with revision, i had considered doing past papers for subjects till i get 100% but 2 of my subjects do not have any other than a set of specimen.
I had considered going through the specification (have done this 3times this year) though seeing the specimen papers show hidden elements to the specification makes me wonder.
subjects i am taking
CS Paper 1 and paper 2 to go
Maths C1 done C2 and D 1 to go
Further Maths fp1 done M1 and NM to go
Chemistry paper 1 done paper 2 to go
Physics paper 1 done paper 2 to go

Currently I'm trying to revise for chemistry physics and c2 as the other exams are a week after those. And I'm just thinking to my self that i have not been able to find an area where i can do any work other than spamming questions for c2 wherever i can find them

I really wonder if theres a way to checklist in a way that will give me maximum marks on an exam, given how different the current exams have been?

Obvious options i considered and am still considering:
Do all the book questions ( by that i mean redo since i have done most in class)
go through practice and specimen papers i have ( what i will definitely do)
past papers of different exam boards( have done around 35 in total has not helped for any part 1 exams at all)
Specification in as much detail as possible coverage.
Memorize textbook (have done this for physics)
alternative sites hysicsandmathstutor revision & questions (mostly questions)

I am in fact considering to do all of this but i feel still variable despite that I know that i need and indication that i can be done and finished with something so i can move on.

Any advice anyone, ps I am aiming for 100% though this sounds more egoistic than i want to be...