1. Put your members content and pages in its own subdirectory. A typical setup would be domain.com/members/.
2.
Strongbox is the most popular security solution that I know of. Many such solutions charge monthy fees, where as Strongbox is a flat fee per site and that includes installation. And yes, it integrates with CCBill.
3.I have no idea.
4. Selling the items may not be the issue. The problem you'll run into is shipping them. There will always be places which it is illegal ship any sex-related item. You'll want to limit your shipping destinations to avoid such puritanical places.
5. Definately see if you can get copies of the IDs of models you've used in the past. Being that you are not in the U.S., you aren't under their immediate legal scrutiny, but you may want to transfer ownship of the site or sell content to an America some day - so cover your bases now.