Regardless of what the seller "wants" to do, he will have to do what the contract calls for. You didn't specify all of the details of your deal, or what is on the contract, but I am going to guess that there is a contingency for obtaining a mortgage on there. I am also assuming you are working with a Realtor correct?
Your Realtor should be guiding you and handling this issue. Please read the contract (Purchase Agreement) and see what is stipulated as far as you being approved for a mortgage. I wouldn't worry too much about what the seller says or does YET, read the contract and you will have your answers.
If the contract DOES have a contingency of a mortgage on there (most do), and you were within those guidelines, then you will be fine, but it may take some doing to get your EMD released. Contact your Realtor to help you and if they can't, contact the Realtor's Broker.
Good Luck and feel free to contact me if you need further help.