I worked for a similar company with the same firing policy for exam failures. The way to pass the exams is to do and redo the question banks, over and over again. You’ll probably get blocks of study leave between your client obligations. So after a day at college, go over any questions you haven’t understood and then practice, practice and practice again. To be honest you don’t actually need to understand to pass, you need to know the method and recognise what to use and when. Things actually start making more sense when you use what you have learnt for the exams at your clients, and this is often quite a while after the exams.