1. pH, nope, don't check it, though I should. For the cheeses I do I find it's not mattering so much at the moment - though it probably would help with mozzarella, which I do on occasion.
2. Kosher salt or non-iodised salt are pretty much the same thing. Other terms you'll find in use are pickling salt and cheese salt. Again, same thing - the point is just the lack of iodine, so the salt is not harmful to the cultures. I've heard some cheesemakers use crystal salt, you know, the rocky stuff, because it's better for the cheese or some crap like that. We have a big bucket of dehydrated lake salt with lots of interesting natural salts byproducts in there - it even has trace amounts of iodine, but not to harmful levels. In fact I think it might have come from the bacteria living in the lake.
3. Don't make camembert, can't really comment. Though what is the second culture you add called? At a guess I'd say it would be a surface culture that would contribute to the rind or maybe the smell?
4. It's always good to have active bacteria, rather than bacteria that have just been sitting around in a fridge for a week or a month, or bacteria spores - hence the use of starters. I wouldn't bother trying to calculate the amounts; bacteria multiplies exponentially, doubling every hour - or maybe every half hour. Anyway, within a few hours you'll have countless bacteria swimming through your cheese - as it should be! Not sure about the other cultures - surface moulds and the like. Never seen any equivalent of yeast calculators.
