I know that you are in Canada and things are higher, but I was feeding my 85 lb GSD beef exclusivley (with rotating veggies), for about $200 per month. I found a grocery store that had frequent sales and an additional discount for buying so many packages at once. I think going non-chicken is important, even non-poultry, including no chicken or poultry fat, etc.
For calcium I did use a mix of Calacium Carbonate (Now powder), and the supplement Nutramin).
I know there are beef based kibbles out there, but I would go with the single protein home-prepared first to see if it's tolerated.
I have a young small dog here, BIG difference between feeding primal preground raw (beef) and the Stella & Chewy's version, very difficult to keep track of all those extra ingredients when you have an issue dog. (In our case, I believe the culprit was the sweet potatoes). BTW, corn in dog food can be GMO corn, which is an allergy promoter, so I would be careful with foods like Iams, particularly if you are feeding with something you eventually want to be safe.