ps will run into trouble if the ph gets out of its range. this happens usually in a cheese like this by too long a warm period in the press.
i believe that some people overdo the whole pressing under whey idea. on many cheeses, this wont have any pronounced effects, but on a ps type cheese it will drive the ph down, which is bad for the ps. you only need to keep it warm for the first hour or so of pressing, after that we want it to cool down and slow down the growth of acidifying bacteria
also about scalding temperature, this is important for the texture of the curd, makes a harder curd resulting in larger eyes
the amounts of the culture here are not that critical.
adding more culture will not mean better eyes.