It's a shame you find yourself in this situation. Just curious when they told you they spent $1800 to correct the problem if you asked to see a receipt of the work they claim was performed? Did you ask them what had been performed and specifically which shop? Also, most used cars I have seen sold in the state of MD have a 30 day/1,000 mile warranty on them regardless of mileage/age. Did your SRT have this coverage or was it "As-is." Should have been an 8 1/2 by 11 inch sheet stuck on the window or windshield. Mandated by the State of MD.
I was also curious, did you drive the car home or did this happen shortly after picking it up? I don't know what to assume when you stated around town.
You have an uphill battle it seems, best of luck getting it resolved.