I've been in this seat both as a seller's and buyer's agent. The bottom line is, it takes approximately 45 days to get a response from the lender's negotiator. And no, you can't contact the lender directly because your name is not on the authorized list of people who can inquire/follow up on the status of this loan.
The listing agent is probably just as frustrated as you are. What you can do is to ask your agent to call your title company and get them to research the property and see what the status is --- has a trustee sale been scheduled? Or has it been sold?
And no... you can't and shouldn't open escrow until after your offer is accepted by the lender who makes the final decision.
My most recent experience with this was extremely frustrating. We wrote a cash offer on a short sale. 45 days later, still no answer.
I called my title company who sent me a copy of the notice for a Trustee Sale. For gosh sakes, the listing agent didn't know! I was the one who told him. (Be resourceful, don't wait for the agent to do the research).
By the time we heard back from the listing agent, the trustee sale was one week away! He hustled to get it postponed. In the meantime, I instructed my buyer that if he still wants the house, to go to the Courthouse and bid. When he got there, he was told that the trustee sale was postponed for 30 days. Again, the listing agent didn't know!
A negotiator was finally assigned. Another 3 weeks go by. Finally, my buyer became extremely frustrated and agitated. After 70 days of waiting for a response, he decided to walk and go in a different direction.
Short sale is not for everyone. If you take your eye off the ball (other listings), you may miss some other good --- or better --- deals.
So....moral of the story....keep looking. Don't put all your eggs in one basket. Don't count your chicks before they're hatched. Blah blah blah.