The bank is the one who says yes/no the the deal... the seller still is the one to "sell" the home but the bank has to approve the loss. Has the listing agent done short sale business before? If he is experienced then having your agent call is most likely no helping and could hamper the process, just human nature. We do a good deal of short business and when the other agent constantly calls it just slows us down and gets irritating. The whole process may take 60 days to get the bank approval, just hold on there... as long as the listing agent knows what they are doing you should be OK.
On the sheriff sale date... that could be a good or bad thing. The bank knows they have until then to decide so sometimes the "drag their feet"... There is a cost to them to reschedule if they put it off so they may wait until the last min. and then expect you to close quickly... I would have my financing as complete as possible in prep. of that possibility.
I hope this helps please feel free to send any other questions you or your agent may have on short sales in general to Mark@MarkRyanGroup.com
And it is the bank who decides what to take, as far as the price goes. You should have all the inspections your agent suggests. In my area that would be an engineer inspection and a termite inspection. Sometimes there are water tests. Your area may be different.