To address your second question - that's just the way PayPal is set up (or, rather, that's the option Store Module is interfaced with - check out PayPal documentation on their site). Since Store Module uses it's own shopping cart (which provides the highest level of control for a developer), it can only pass the order's total and some description (thus the Shopping Cart name property in Store Administration). It really utilizes a Buy Now button option.

If you want a detailed PayPal process, you'll have to either use their shopping cart or interface with a new web payments option they've introduced recently. Both would require some programming and changes to core module.

IMHO, it would be by far simpler to sign up with Authorize.net