I fed my puppy the same amount up until 12 weeks. I was worried about his weight, and asked the vet. She said to feed him as much as he wants. I don't do that, because I would like to have some food left for myself, but I eventually settled on 1 1/2 cups 3x a day. I would think he will need more than 1/2 cup before too long.
Our vet recommended us to feed the pup as much as he wanted to eat for up to 15 minutes a day when he was younger. He ate quite fast so we made it 10 minutes. We soon realized he would keep eating if we kept adding food to the dish, and when we saw he was getting a bit chunky, we started measuring the food a bit more. After a couple of months we fed him twice a day about 2 cups of dry, mixed with some wet food. But he remained a bit chunky, so I have made it about 1 1/2 or 1 3/4 cups twice a day. He is not very slim, but Its because he doesn't excersice as much as he can :/