Paypal doesn't allow adult transactions anyway, and MFC tokens are a non-refundable service. Pretty much all adult sites and most retailers use credit cards.
MFC is a huge company; they dont care to steal your credit card account. They use secure transaction companies like CCbill, Zombaio etc.
No random person is going to get that credit card number unless you're using an insecure internet connection that someone is actually bothering to monitor and decrypt, or you have a keylogger on your computer (these things are pretty unlikely).
Are you worried about your wife seeing a charge on the credit card bill? Get your own credit card or buy a reloadable prepaid.
Or are you a minor and cant get a credit card? In that case, wait a few years and go enjoy some tube sites.