Hello,
We currently do not have an IPN variable which informs you whether a payment was made by a credit card or by an account's funds. We will consider introducing this variable.
Has for your second quesiton, I am not quite sure what you are referring to when you mention "click credit card button" as we only have our Buy Now button which allows the user to choose between using a credit card or the funds in their account to complete a purchase when they reach our Pay Process page.