1. This can depend on the PayPal options allowed for your particular country. Some countries don't allow the credit card payment option.
2. Refunds between whom? If you have charged someone for job listings on your site, and they have paid but then change their mind, then refunds would of course be at your discretion.
3. JobRoller allows 2 different registration types, job seekers and job listers. All of these users will appear in the "Users" section of your WordPress admin. You also have the option for admin to be bcc'd in on all job applications via your JobRoller site.
4. Not by default, this would involve some customization of the theme in order to do this.
5. As mentioned aboved, user information is contained in the "Users" section of the
wp-admin, so if you wanted to use these and form a mailing list this is not a function of JobRoller.
6. There is no specific option for this built into the theme, so again, this would require some customization on your part.