I am sorry to learn of this situation.
As you have 3 separate formal legal opinions on the matter, I would go with them (obviously we cannot provide you with that same level of assurance, but in general, I would agree with their assessment of the matter).
His understanding of the law (even with his degree) is somewhat tortured - CA small claims actually has a cap of $10,000.00 (while I am sure you don't want to bring this to his attention, I only raise it to illustrate the fact (and confirm) that he is only trying to bully you into paying for his car.
Fortunately, small claims court is relatively informal and the California Courts have a lot of information to help you.
The small claims self help site has information on how to defend yourself in this matter (the most important thing is to make sure that you actually file an answer - you don't want to ignore the summons and let him win "by default").
The self help site (here: http://www.courts.ca.gov/selfhelp-smallclaims.htm) has all of the forms you will need - along with a great deal of information about how to represent yourself at your hearing ("trial").
I also recommend trying to go to the courthouse a week before your own hearing and sitting in on the small claims docket, this gives you a much better idea of what to expect of the hearing and help you better understand the process and procedure for your own hearing.
The hearings are fairly informal, but there are rules and procedures (the self help site describes these fairly well).