general rule that i follow is to feed the tort as much food that imaginarily cover it's shell.I feed my torts(which are not sulcatas)twice a day, first meal is big one while other one is a bit small.For detailed info you can refer to TOM's threads.
Feed a big hand full. If he eats all of it. Then the next day feed him a bigger handful, until you have given him enough that he has some left over. Then that's the amount to give. I have a leopard. I would always make sure he had some left over. He would usually eat the rest later in the day.
I feed twice a day, once in the morning and once in the late afternoon or early evening and he has access to fresh grown grasses, clovers and weeds all day. This way he can eat as much or little as he wants.
My guys never run out of food in thier Habitiat. Every morning I toss the leftovers and replace with fresh. If they are outside.... well... they never seem to run out of grass....