The puppy needs to eat for growth.
A puppy that is so food motivated, can also become food aggressive if you put too much attention on the food. I would set his food down and let him eat it, and use something else, cheese or meat for potty treats or training treats -- JMO.
A puppy that is so food motivated CAN overeat and it can actually kill him. Unlikely. But a pup that wants to eat everything in sight can easily over-eat to a dangerous extent if left to "free-feed."
Also, going off the feed is the best way to know that a dog is not doing well and needs to visit the vet, you do not always figure this out as fast when free-feeding.
And, there's the pudding poo. Usually a sign of over-feeding, but it can also be something like coccidia. If you free feed and he seriously over-eats he will likely get ful blown diarrhea. The problem with that (beside the inconvenience and mess) is that the food shoots out with most of the nutrients intact, so the dog is eating a ton and literally starving.
And for a pup his age, a strict schedule with food and potty breaks is the easiest way to train them, which makes free-feeding a problem for house training.
If the puppy is eating all its food and looking for more, increase the food by 1/4 cup/feeding. If you want to improve the stool, add a teaspoon of pumpkin to his dish. Usually though, even if they have a little bit of a pudding poo, when they get used to the larger amount, that will clear up.
The puppy is light for 11.5 weeks. I do not agree with young puppies having waist lines and feeling the ribs. Sometimes you can, they just have trouble gaining weight, so you do your best. But letting them have a little weight on them is a little healthier, because they are growing. The amount of growing they are doing is staggering. A human baby is born at what 7 pounds and by a year old, maybe 20? Well, that puppy is going 60 usually by a year, and maybe 70 or even 80 pounds. It's head is going to grow so much, it's no wonder puppies are a pain, they are IN PAIN, growing all the time. They go from 1 pound at birth to 70 pounds in 12 months, easy.
And they need to eat, a balanced diet. Usually a balanced diet for an adult dog is fine for a GSD puppy. But a lot more of it than you would feed your adult dog, sometimes double, not double what you would feed a 75 pound shepherd (not at first), but if the dog is 12 pounds and it says 1-1.5 cups for an adult 12 pound dog, than a puppy would probably need to eat 2-3 cups, and as it grows, that food increases. By six months that puppy might be eating what your adult shepherds are eating, and maybe even more. It's growing. It is up to us to keep up with the growth.
It is possible that your pup got pushed off the heavier producing teets, and maybe didn't get the lion's share of the kibble when they started feeding solid food. A lot of folks have the opposite problem, the puppy misses the competition at the food pan and doesn't want to eat. Yours does, that is good. But it sounds like he needs more.
Also, puppies have more energy than adult dogs, they spend more calories because they run more and the sleep more and so besides growing they are feeding puppy energy, so its a lot more food. But it also something that a feeding range cannot always calculate. That is a place to start. It sounds like yours needs more than that, and that's ok.
Lastly, we want to feed our dogs the very best, so we research and find the best food for our puppies, and sometimes that works out great. And sometimes it doesn't. Fromm is a great name, and a lot of people swear by it. Your dog may not like it, or his body may not thrive on it. Just something to keep in mind. Sometimes you have to go to your second or third choice before you find a food that he likes and that is giving you the results you want.
