Wow, calculators were around in the 60's? I remember in the early 70's my dad had a calculator which he kept in the top cupboard. None of us kids were allowed to touch it because it was too valuable. My how times have changed.
I did ATPL Nav in 2006 using AFT and was quite amazed how close the practice exams were to the actual CASA exam. I remember there was one question that used an NDB in WA as a fix, but that NDB had been decommisioned which made the question redundant. And if I remember correctly there was even one question which repeated the same choice (eg, choice A and C were the same). Ah the joys of sitting ATPL exams.
I suggest you get in touch with team at AFT. I believe their policy is to continue supporting you until you pass. Good luck.