About the billing fields, you probably have this attribute in your shortcode:
ns="1" The no_shipping directive. Possible values: 0 = prompt for an address, but do not require one, 1 = do not prompt for a shipping address, 2 = prompt for an address, and require one. Applies w/ PayPal® Express Checkout only; because Pro Forms do not ask for a Shipping Address. However, you may request a Shipping Address by creating Custom Fields under: s2Member -> General Options -> Custom Registration Fields. Not valid when cancel="1".
Other attributes relevant to PayPal Express Checkout are:
# ps="paypal" PayPal® checkout Page Style. Applies w/ PayPal® Express Checkout only. Not valid when cancel="1".
accept_via_paypal="paypal" Accepted Billing via PayPal®. A comma-delimited list of Billing Methods you want to accept through PayPal®, as opposed to processing them on-site. Due to a PayPal® policy, you may NOT exclude PayPal® from this list; s2Member won't let you. Tip: If you don't have a PayPal® Pro account, you can set accept="paypal", and accept_via_paypal="paypal,visa,mastercard,amex,discover,maestro,solo". With this configuration, all you need is a PayPal® Standard account with Express Checkout ( which is free ). Not valid when cancel="1".
Let me know if these help. If you still have trouble, could you let us know with more details about your problem? What you cofigured, where, etc.? No private/sensitive information, though. Thanks!