I've been very pleased with the Victor line of grain-free. If you can find it, it's an excellent choice. The ONLY kibble I'd prefer to feed over Victor is Orijen...but it's crazy expensive here, and when I did try a small bag Logan has diarrhea on it. He hasn't had loose stool with the Victor unless he gets into something else he shouldn't (like catching and eating starlings
). I pay anywhere from $36-$45 for a 30 lb bag of Yukon Salmon and Sweet Potato GF Victor. I get points every time I buy food and then I get discounts with points.
Would a pre-made or ground raw work for him? Pre-made from a store might be insanely expensive for a dog his size, but you could give it a shot, and if it works, invest in a meat grinder and grind your own pre-made raw for him. Or you could try something like Honest Kitchen or Sojos.