I'm sorry to hear your story, although it is a very common one. The fact is that home prices have continually decreased and therefore have brought down the value of homes even if they aren't for sale. Some lenders will allow you to have more than one appraisal. I went through this about six months ago and we were able to get a second appraisal - we had to pay for it however - and the bank also allowed me to submit a market analysis.
Along with that, I had my clients take pictures of all of their updates and attach the receipts of those updates. We sent that along with a detailed letter of the updates and the second appraisal came in just high enough to allow my clients to refinance.
Keep in mind that appraisals are not an exact science. They are a calculated opinion. I would pursue your lender one more time.
At the worst end, you should take that appraisal to your municipality and apply for a tax reduction based on that new appraisal. I have clients who have been successful at getting their property taxes reduced.
Hope this helps.