how much pressure can they take?
For pressure : 590 kpa = 85 psi = 5,86 bar
From experience (of other guys, not me), the HP 406 can accept 30% pression more but Panaracer prefers to be prudent with that.
As the tanwall versions are 66 TPI (instead of 27 for the blackwall version), the tanwall versions are liable to accept more pression than the blackwall. Actually these tires are already considered getting a "tough feeling" after 5 bar ( = 72,5 psi)
TPI : thread per inch, that's about the weaving of the tire and precisely about the density of threads there.
For your others questions, maybe you have to find japanese riders here or in other boards to get a opinion because it has been said that these tires are largely used in Japan..