I am right that you are divorced? If so, it's not your problem and jsut returning the mail or telling callers you don't know where he is should be enough. You are not liable in anyway if you are no longer married. Personally I would not contact him because it's not your problem.
If he did file for banckruptcy, the creditors would not be trying to reach him since all that collection effort gets put on hold as soon as they creditors are notified of the filing.