To answer your other questions, yes, it could make a bonsai. I'm a novice myself, but have gained a few years of experience.
You have a couple choices... keep in the ground for faster trunk development, or dig it up in spring as the buds begin to swell and put in a grow box with good bonsai soil. A third option is a bit more for when you gain experience... to use it for air layering into many trees.
I'm in Southern CA, but lived in Davis for a couple years, so I understand the Sacramento summer heat. The heat and dry air are probably what got the leaves all crispy. I've found that mine are best kept in dappled shade under a large tree. The ones I've had out in the sun always get crispy at this time of year, which screws up my fall colors.
If you decide to leave it in the ground, just learn to take better care of it. Fertilize, water properly, keep the bugs at bay, etc. Let it grow.
If you decide to dig it up in spring, you'd probably also chop it down. It will sprout new branches in spring and summer.
The good thing about J. maples are that they are widely used and understood in the bonsai world, so there's tons of info out there. However, you've already landed in the absolute best resource, bonsainut.com!