It's always a bad idea to buy Italian cards on eBay...
You probably won't have the chance to refill the card with an American credit card, you won't use the Blackberry without a Blackberry contract and you won't be able to register to the very useful 155.it without knowing the details of the registration of your simcard (which should be your details, but who knows...).
My advice is always the same:
BUY ITALIAN SIM-CARDS IN ITALY. It's cheap, you can activate Call Your Country (cheaper international calls) for free and most of all it will be regularly registered with your details, with no problems for you (and the 155.it) and without breaking the Italian law...
Now, ask the seller about the registration. Did you give him copy of your passport? I won't give it to an unknown person, anyway... If not, ask him the details of the registration, including CODICE FISCALE of the registrant. With those details maybe you can register to 155.it.
Then you can try to register on Mondowind.it, all in Italian of course but we can help, and try to refill with your credit card. Sometimes it works, usually it doesn't.
About the Blackberry, I honestly hate those phones and I'm not an expert at all, but I fear there will be no chance to use it for data without a specific plan (business, postpaid).