Insulating a Wall Against Unconditioned Attic Space
I am not clear at all from your description how your rooms are laid out.  One thing I'd try is not on your list I'd install an attic fan on one of the gable vents with a thermostatic control.  This will keep the attic from getting much over the outside ambient temperature.  This will probably be money well spent even if you have to add insulation etc. as well.
Outside the box - solar on the roof might give actually take that radiant energy and turn it into electricity and money, rather than nuisance heat in your attic.  I don't know what the current situation is in California but I think at one point the subsidies / incentives made solar a good buy for the homeowner.