What you describe is a highly compromised short sale situation. Short sales are the 'Wild, Wild, West of Real Estate" where there exists an illusion of rules but anything can and does happen.
All you can do is try but, you should be prepared for almost certain disappointment after investing patience, self-control and hope.
Consult with your real estate professional in regards to your plan B if this is the ONLY home for you. In six to eighteen months this home will be available for purchase again. At that time you will need to act decisively and at the speed of light. Many, who are seeking a home to live in, opt to find another home to purchase. ANYTHING CAN HAPPEN! However, what is most likely to happen is not favorable to you owning this home through a short sale purchase.
Best of success to you,
Annette Lawrence, Broker/Associate
Remax Realtec Group, Palm Harbor, FL
Best of luck to you in your home purchase!