This is what they're gonna do . . . they file the lawsuit in SD knowing you aren't going to go there and fight it. Then they get a default. Now Tremont isn't going to do things properly which would mean to hire a California attorney and bring a second lawsuit to enforce the SD judgment. They're just going to send a copy of the SD judgment to your employer and ask him to garnish it from your wages. Since it's a court order, your employer won't want to run any risks so he'll probably just comply. At least that's what they're counting on.
So what should you do -
1) File your own small claims action against them in California for overcharging you. Since they went to court they waived any arbitration clause in your contract. Besides they won't even fight. In addition to money, ask for a court order "denying effect to any foreign judgment rendered regarding the alleged loan." (My brother in-law, the amateur attorney, came up with that phrase.)
2) Let your employer know what's going on. It may be embarrassing in the short term but it's better than them getting your paycheck.
3) File complaints with the California Department of Corporations as well as the AG. Corporations licenses deferred-presentment transaction providers and has gotten very aggressive over the last few years.