Correction: The Bank of Japan is trying to increase inflation from about zero to two percent, understandable after some twenty years of deflation. However it may well overshoot its target by a considerable amount. It is very difficult to know when to stop when creating money from hot air.That is correct. Japan has only budgeted for 42 F-35A's with the expectation that they will come into service early 2020's. However the timing / numbers continue to be evaluated by Japan due to the deflationary measures being taken on the economic side of things.
I'm not sure where the idea came from that Japan would be operating JSF in any number off of their recent Helicopter 'Destroyer' designs. Capability to do so is in question but more to the point no F-35B's are on order. If that were to change in the relative near-term, we would not see operational F-35B's in Japan until end of the next decade best case.
Cheers,
Zool