Ed, I think it is really possible that your Cali King is pushing its limits and seeing just what it can get away with. Since you are now feeding it properly and it is gaining weight and strength, the most important thing in it's mind now is to avoid "grabby hand" and being handled. Kings and Milks are very well known for being bitey and flighty, though I have seen several that are very mild mannered and perfect gentlemen and ladies. These particular Kings/Milks have been handled every day save for feeding day and the day after. The handlings don't have to be for long periods, either.....15 minutes every day seems to help.
My suggestion would be to wear a t-shirt around all day long and then place this near the hide where your Cali King hangs out the most. Leave it in there for a couple of days and allow it to get used to your scent. Maybe this will help it to realize that your scent is associated with home and that you aren't as big a threat as it thinks.
On the matter of feeding outside of the enclosure...some do and some don't. I feed all of my snakes in a separate tub because I found that feeding some of them in the enclosure made them very cage defensive. This was especially true of my BCI boa, who had never tried to bite me even once until I made the mistake of feeding him a couple of times in his enclosure. However, with my Corns, they don't rightly care where I feed them, just as long as their getting fed and I haven't had any problems with feeding them in their enclosure when I've been rushed to get feeding done. It really is a personal preference. You could maybe try feeding it inside of the enclosure, to see if that helps with the aggression....and if it doesn't, maybe go back to feeding in a separate tub or whatever you prefer.
At any rate, I think if you keep up with your gentle handling and don't allow the snake to "cow" you (ie. don't back off and put it down if it bites you, this just teaches it that biting gets it free of you, etc.), then with time it may quiet some. Though the others are right...there are just some Kings and Milks that have that quarky personality that make them real buttheads to keep.Best of luck!