Sounds to me like the catylatic converter is plugged. My Dad had a doge d50 with a 2.0 and had a lot of the same symptoms you are having. A new cat and it was fixed. However I would remove the oxygen sensor and inspect it for fouling do to the oil situation you spoke of. You may try cleaning it if dirty or just replacing it (~$50). Possibly on the con the exhaust pipe or cat where crimped. Good luck