Stop relying on Credit Karma. You may think you have a somewhat decent score just because they show you a 660, but your FICO may be way lower, and the lenders you will encounter will be looking at WAY more than just your mediocre score. All the late and slow pays you've had recently due to your "friends" paying late are going to haunt you here.
You're $5000 or so upside-down. Auction value on that Impala is about $1500. No matter how they structure the numbers on paper, that's the amount they're going to give you. They can show you more for the trade on paper, but it'll be added back in to the numbers somewhere... they'll need more down, they'll add more to the loan, they'll up the price on the Chevy. You are buried in that car. Even if you had the cash down needed to erase it, you'd be THROWING THAT MONEY AWAY. That large of a down payment should be going toward lowering the overall amount financed, so at the end of the lease term (again, assuming you'd get approved) you walk away with nothing and lose every dollar of that down payment.
Leasing is for folks with excellent credit. It's not a quick way to a lower payment. With your negative equity, you're gonna find that your payment on the lease (assuming they would even allow that much negative equity on the loan/lease) is going to be much higher than you think.
Again... there is no magic way out of negative equity. The salesperson can chat you up for hours about it, but the lender's gonna shoot it down. Mediocre credit and negative equity don't equate to a lease.