If I was in your position I’d schedule one or two less weekends with the car and get a used clutch kart. The F100 group seems to be growing in So Cal and you can run practice days or race pretty cheap.
If you sell the car and go with just karts you’ll probably miss it sooner than you think. If you get a kart and keep your car you can do either and more seat time will make you better no matter what.
That is unless you have someone telling you that you have to choose ;-)