I have managed to fail the actual exam big time
I'm sorry to hear that.
And I know the subject
To be blunt, you obviously don't. You haven't stated which text books that you have used to study, if any, you have only mentioned the exam practice stuff that you have used.
md 600 driver is quite correct to say know your subject. Most exam prep books/software simply require you to demonstrate that you remember in a simple way what you have read. Although the actual exams do have straightforward questions for equally straightforward answers, there will be a number that will require a practical understanding. The provided choice of answers will often be i) completely wrong ii) partially correct only iii) wrong but very appealing (usually the longest answer) and iv) the correct answer. If you rely too much on question and answer books you can easily fall victim of 'find the lady' a card game which is hosted by con men.
The real answer = read the relevant manual for the subject and understand it. I would also recommend an hour or two with an instructor.