Well here is how I see it from a buyers agent side, basically what I see is that the listing agent wants to get an offer into the bank so they can get the procees started, they also state that they are still taking back up offers this keeps the process going. Once you get a BPO done by the bank and have what the 2nd will take as a pay-off this just becomes a regular sale time wise,so if the buyer backs out you have back up offers and go from there. I have also seen listing agents demand the buyer make the 2% or 3% deposit in escrow as a way to keep them more committed. And basically you ask the buyers agent how committed the buyer is to your property, of course you won't always get the truth, but it never hurts to ask.
I hope this gives you some ideas to work with.
At your service,