This is not the type of problem researching Dobequest is going to help and not the type of breeders who are able to help.
I suggested a decent large breed puppy food that will grow your pup up to be healthy and should be in the same price range as what you were feeding. Again many people on this board have raised their puppies on this food with excellent results.
There are several others you can choose. Orijen LBPF is the best, but you will pay dearly for it...again it is the best dry kibble out there. Acana LBP is okay, but not a whole lot better than the Innova, imo. Nature's Variety LBPF would be another one I would recommend. Between Acana, Innova, Nature's Variety, there is just not that much difference.
You can also feed an adult kibble, but only if it states on the bag that it is an "all life stages" food.
I was just trying to keep things simple.
You can feed him a boiled egg once a week and give a couple of bites of cooked or raw meat with his evening meal. At his age, I would lightly cook the meat as you could have a problem with salmonella if he ate any contaminated raw meat, unlikely it would cause a problem, but it has happened to puppies before.
I would start giving him 500 mgs vit c right now after his morning meal. If it makes his stools loose, break the vit c in half and give 250 mgs. In a couple of weeks bump it up to the whole pill or give the other 250 mgs after the evening meal. When his is around 4/5 months start giving 500 mgs after morning and evening meal for a total of 1000 mgs of vit c a day. Keep this up for the life of your dog. I also suggest adding fish oil or krill oil at around 5/6 months or so. You can give human vitamins of c and fish oil. Give him a 1200 mgs fish oil pill every morning for life. When you give fish oil, you must give vit e as fish oil depletes the body of vit e. Give 200 mgs morning and then around 8/9 months you can add to the evening meal also.
Try reading the DogAware site below about suppliments. The ones suggested are what I recommend as a minimum and give my dog every day plus others.
Read this for dog food education: Choosing a good kibble (dry dog food)
I have two sites below which you can research foods.