I feel your pain, living in "Cattle Country" of Alberta, it is hard to find decent milk. Out of the 10 times I have tried, I have had two successes with store bought p/h milk, and they were "ok". I did get good mozzarella some milk from Vital Green Dairy out of Picture Butte Alberta, they low heat pasteurize, and it is whole milk, not homogenized. If I can remember, it was about $14 for 4Litres at Earth's General Store in Edmonton.
Have you tired Goat milk? Happy Days Goat Dairy low heat pasteurizes and may work better. I have yet to try it, I have to add this to the list too.