I don't think you can accomplish what you really need by just linking a credit card, as in order to recieve payments they will only go into your p/p acct. you won't be able to transfer them anywhere's, so they will sit there, they can't be dumped to your credit card.
You really need to become verified, and toss the $.03 to them to upgrade to a higher level seller account status, which does require linking a checking account to it. As a feature then, you use that account to back your purchases/transactions, and not the credit card.
P/Pal is VERY secure, if not TOO secure. I have been a seller status account for years, and never had issue. It's almost impossible to hack them, your bank is easier to hack, and as a fact I have had 5 different bank credit cards replaced by my bank in advance of a "hit", simply because THEY were compromised, and generated a generic "you may have been" mailing, which forced a new card, and account number on me.....that sucked, as I then had to re-establish about a dozen automatic payment accounts each time, very inconvenient for THIER poor security measures.
so, in a nutshell, I trust P/P, and can say I never worry about them.....my bank on the other hand.....needs better countermeasures.
it's all splained on the p/p site as to what is needed for each level of status, and as noted, if you are aprehensive, simply open a designated checking account with $50 in it solely to link to p/p.