AFAIK the answer to all of your questions is yes. Although I'm not sure to what amount of checking dish does, I'm sure if they see that 2 receivers on the same account are reporting from different IPs, you will probably be getting a call from the Verification team. There would have to be a fair amount of leeway on this as the receivers probably do not contact dish at the same exact time, and Many ISPs give out temporary IP addresses that can actually change quite regularly. Along the same line, anyone familiar with VPNs could probably game the system a little easier than the phone line system.
Although I have never tried, I would think the ability to bill PPV has to be integrated as you can order VOD via Ethernet. The only thing I know of that you cannot do via Ethernet are the services offered in Dish Home interactive, and those abilities are comming "soon".