Oh man, the great food debate. As someone mentioned earlier the calcium content is important to keep your eye on, but what actually matters and what the studies have proven is the Cal/Phos ratio. Many foods don't tell you the phosphorus content so the best guidance is to look for a food where the calcium percentage is around 1.2% (If I remember correctly). There are also a ton of resources online that can not only guide you to the proper percentages, but that actually list the different foods that meet those benchmarks.
Something to be cautious of, foods that tout being grain free are often very heavy on the legumes. The problem is legumes are a high protein filler. So while they might be a high protein food in the sense they can list 30+% protein on the bag, exactly how much of that protein is actually animal protein? These companies claim that "dogs are carnivores they need meat, not grains" but then turn around and provide a food where as much as 50% of the protein content is coming from plant based sources. Yeah, that's makes sense. I look for a company that will tell me the percentage of protein that is animal based. I would much rather have a little lower protein content but have 90% of that protein coming from animals. Then to feed a protein percentage 3 points higher, but have only 70% from animal sources.
Also, named meat meals are not bad. In fact you want to see that listed as a first ingredient. "Deboned chicken" or whatever sounds nice, but remember that foods are listed by weight preprocessing. Unprocessed meat is 70% water weight, so when that meat is ground up and dried/cooked it falls way down the list. You do want to see the actual meat meal named though, lamb meal, chicken meal, etc and what not. There are regulations that govern what can be included in named meat meals so the typical garbage in unnamed meals will not make it into your food. Watch for ingredient splitting, which is breaking down ingredients into their different named parts so they fall down the list of ingredients. You'll see it a ton with legumes. You'll see "red lentils" and then two or three ingredients later "green lentils", yeah those are both just lentils and if you combined them they would jump much higher on the by weight list of ingredients.
Grains aren't bad, dog's digest them just fine when they have processed like all kibbles have been. As they say everything in moderation and that's what you want to see for grains in your dog's food.
You want to see quality meat meals and meat products listed predominantly as the first 4 ingredients. I will not feed a food that doesn't include a named meat meal as the first ingredient, and that doesn't have meat products as 3 out of the first 5 ingredients. Personally, I have found the most success feeding sled dog foods. Dr. Tim's is my go to brand, and Dr. Tim himself is readily available to have a chat with you.
As for taking the puppy at 6 weeks, please don't. In fact in the vast majority of states in this country it is actually illegal to take a puppy from it's mother until 8 weeks. I would be very shocked if New Jersey is one of the exempt states. 6-8 weeks is a crucial developmental period in a puppy's life, this is the time when they learn bite inhibition and other social skills that make a very confident and well adjusted dog in later life.