I also just want to say, I am very sad for you that this is your home buying experience. Good luck.
You should investigate the source of the problem. Is it a support or possibly a slow leak somewhere,.. That would be my first step.
The latest earthquake technology has determined that the builder best suited to surviving an earthquake are not solid, strong units, but rather flexible units that can roll with the punch.
All houses develope cracks; I have never seen a house that didn't have some cracks.
The inspector was determining the condition of the house AT THE TIME of the inspection: He determined that there was nothing serious. He cannot be held accountable for the earth moving 10 months later.
And even if he could be held accountable; what are you going to sue him for?
Or the previous owner?
Good luck and may God bless