I would be interested to know more about the regulatory aspects of this. Are you registered as a money service business, or whatever the hell people in the USA have to do to transmit "money"? If not, and you believe you don't have to, what is the name of the lawyer who you have on retainer who gave you this advice?

What do you mean by you're "FDIC insured" - did you get the FDIC to insure all your USD holdings? What about the BTC holdings, will those be insured too?

I think your testnet/have-at-it approach is a excellent one, but there are some huge unanswered questions about this site's ability to operate inside the USA. I think I'd rather take my chances with hackers in Chile or Japan, than with the authorities right in the "belly of the beast" unless you've dotted all the Is and crossed all the Ts.