I have several Cal Kings and they're great little snakes.
I would ditch the light, leave the thermostat for the UTH set so the hot spot is 88*F, and put a hide over the UTH as well as on the cool side. You'll find they like room temperature, unless your house ambient is around 60*F. I use aspen as substrate as they like to burrow.
Unlike a BP these guys don't need to be super humid to have good sheds. I mist mine lightly each evening.
It's all too easy to overfeed a Cal King. Its body shape should be more square than round. If it's round it's fat.