You can always sit out there and talk to him every night, while there's a can of food about 2 feet away from you. Leave 1/4-1/3 of the can out there when you go in; He doesn't get the whole can unless he comes out while you're talking to him. Leave him a cup of dry food and water every day no matter how tame he acts. Make sure you rub the dry food through your hands so that any he food he eats smells like you. Eventually he will learn that you mean food, and that visiting while you talk to him gets him lots of GOOD food. Once he's regular about getting the canned food, set it closer and closer to your hand until you can wiggle your fingers and pet him. Eventually he will be a pet, though maybe never a housecat.
I've done a couple of stray cats this way, but they were dumped cats and not truly feral. But if your boy is sleeping in a car seat, I'd say he's a scared dumped pet and not feral.