Sure did explain his motivations all season long. It did seem odd that a guy as seemingly cold-blooded could otherwise appear to be a good dad.
I'm still concerned about one thing - so far, all of Isaac's premonitions come true. Short of Hiro rolling back time and undoing Peter's explosion - I don't see the explosion being stopped - just - dealt with. In Peter's dream, he sees New York *evacuated* - and then he blows up.
I read somewhere that Hiro goes way back in time next season - and possibly IS the Japanese hero he emulates - if that is true, perhaps the season ends with him doing some incredible time-space thing. Of course, if he goes back in time with that damned sword, I will wonder where the thing came from in the first place.