You scare me when you say that the sale has been approved:
Whom has it been APPROVED by; the SELLER or the BANK?
The Seller, in a SS is really a "rubber stamp" approval.
You really need the Bank's approval, and if you have it, there will be no problem for the time-is-of-the-essence, because the Bank will want a long Escrow.
You will not receive a SIGNED acceptance, such as you would get from a normal seller:
you will probably get an ADDENDUM or a COUNTER OFFER for you to sign, and the Escrow will be opened.
The LISTING AGENT is working for, and chosen by, the Seller, so the Bank will not treat him the way that they do with an REO. Communication may be lacking.
Good luck and may God bless