Thanks guys, that answers my question about the holes.
Regarding the PVC, I did read the wiki and a number of the threads here regarding the pros and cons, and after a bit of research, reading MSDSs and so on, I decided the risk was minimal at worst and opted to use it for the time being.
There are many different types of PVC in use, including the cling wrap used throughout the food industry. From what I've seen, the primary toxic culprit in the material is not the PVC itself, but the phthalate plasticizers added to it in many applications in order to make it flexible: shower curtains, furniture, car interiors, kids toys, inflatable what-nots, etc. While I've found many articles about the dangers of these types of vinyl leaching and off-gassing, I'm not finding anything about PVC piping, which is designed specifically to be inert in contact with a wide variety of strong acids, alkalis, salts, alcohols, etc.
Given the short amount of time the curds spend in the hoop, I'm willing to take the risk for now (until I can afford to lay in a stock of proper hoops) but I sincerely appreciate your input and concern.