Legal Question in Appeals and Writs in California

Nope. Once he elects to the limits of small claims court that's his recovery. Good luck.

No, unless the new claim is about different facts. If the defendants wronged him twice and the small-claims case concerned only one incident, it won't block a lawsuit about the other. But it will block a second lawsuit about the same incident.

The rules are not as simple as my answer suggests, since it's not always easy to draw the line between claims which are too closely related and those which aren't. If your son has doubts, he may want to discuss his situation with a lawyer.