The shopping across state lines is problematic if you don't have any controls on the insurance industry, because then all of the insurance companies would relocate to the state with the least consumer friendly insurance laws. But I heard that that idea was included in the bill in some form (I could be wrong about that, but it's what I heard).

A tax credit is not the same thing as a tax deduction. You can get money from the Treasury with a tax credit even if you haven't paid any tax. The Earned Income Tax Credit is one such credit.