Unfortunately fractional reserve isn't safe for a currency that is this volatile. Depending on what the "fraction" is, some major withdrawal demand against one of these exchanges would topple it
What's the Big Fish to do?
a) Quietly keep pressure on the exchange, taking the money as it comes, while not putting any back into the exchange.
b) Make a big stink, bring in lawyers, write press releases and bring down the exchange, possibly destroying any opportunity of getting the money back.