I forgot about this thread. I've made some mozzarella a handful of times, not as much as I thought I would, and for some reason the first time had been the best. I had large curds that were easily separated and it was very easy. The second time was all ricotta. The rest have been varying degrees of curd size but I always was able to get mozzarella. In some of the batches, I would have a fair amount of whey to separate out each time I heated the curds and it looked like I would get only ricotta like cheese, but it worked out. For me some of it may be a patience thing, but I think a lot of it is ph. The recipe I use also calls for less citric acid, 1 tsp and also no CaCl2. I've used organic pasturized, not ultrapasturized, milk from Wegmans for every batch. The 2 tsp may be for raw milk. From what I read the curds dont form as well if the pH is too low.
I also got some ricotta after making the mozzarella by heating and straining. It wasn't a lot but it was worth it.