If I were he, I would:
1. Analyze the past transactions to work out how much has been lost to errors
2. Figure out how much is recoverable by fixing the broken trades, i.e. how much has not yet been withdrawn, and also decide whether this is ethical
3. Figure out how much is not recoverable, and whether the business has enough reserves to cover the losses
4. If not, figure out if he can prop it up somehow or whether he must declare bankruptcy
5. Overall, limit his business's exposure to lawsuits down the road, either people who disagree with the outcome of (2), or people who feel robbed due to the exchange's downtime and freezing of their BTC during a crash, or... etc, the richest people will find many reasons to sue
6. Plan how to restart the site without bugs or bad publicity
To me, that (2) is ethical or fair is not obvious. It is a very difficult situation. See (5).
Yeah, this looks reasonable. Except the patient thing. I need him to say something in order to know what to expect.