To clarify, if this is a true balloon loan, the OP has purchased the car, but structured the loan much like a lease. That means he owns the car subject to the lender's lien.
The problem for the OP is that he needs to do something. The loan terms are awful and it makes no sense continuing with the loan, even if he wants to keep it. Very little of the payment is going to principal and the longer you have the loan, the worse off the OP will be. A co-signer may be required if financial situation is an issue, but at today's low interest rates - as low as 1.5% for a refi - OP could pay off the entire car in 5 years at a similar monthly payment. If OP can't refinance, selling it now, even at a loss, would be wise.
OP - how much is the current payoff? I would think it's ~47K.
If it were me and refi is an option, I would certainly keep it. It's been babied like none other. Just look at the other e90's out there sitting - high mileage, vague sellers, etc. - it's not surprising they aren't going quickly. I transferred the lease on my 2011.75 e90 recently and there were several serious buyers. But ultimately OP needs to make the right financial decision and a sale may be the only option.