I have found to get to the FM level in the main rulebook for Brit Paras you need to multiply by 1.5 not 1.33.
I always assums that covers the superior JL and the 6th dice?
Well, the ratings in the book weren't worked out using the CoCulator, which is why they got revised when the CoCulator was published. The basic para platoon is 96pts, which bumps up to 128pts for elite. That's +7 and then the sixth dice pushes them up to their actual +9 rating. There's no adjustment for superior JLs.
Yes it does the 6th dice for elites was in the last errata 2017
EDIT: To be fair the errata 6th die is slightly different in that 5's count. I have to admit we play the elite 6th die the same as the red die as they both cost 2 points and it keeps it simple to remember.
However, not sure what Rich's thoughts are on the difference.
TT,
Rich has commented before to the effect that the difference between the red dice in Blitzkreig and the 6th dice for elite units as amended in the errata is intentional. The truly elite units keep their ability to generate a Chain of Command dice quicker. Such units should be rare, however, and I prefer to use the red dice version too.
If grading a platoon 'Diehard' is there a cost on the co-calculator? I've looked back but it's an awfully long strand!
No, that one's not covered. To be honest it's such a massive boost that I would only use it in very special scenarios. It's not something you'd want to use for a casual game.