P0306 code turned into almost dead engine

Okay so I need some help here. Let me start off my acknowledging that yes I was a moron and drove on the car with the P0306 code and random misfire and I understand that is why I am writing this today. On March 17th 2018, my 2003 civilian crown vic started shuddering when I accelerated heavily. Didn’t think anything of it until about 5 days later when is threw a CEL. again, the problem was still intermittent when I first got the CEL. On Thursday March 22, I had autozone read the code and was informed that I had a misfire in cylinder 6. They recommended replacing spark plugs and coils. The misfire started getting worse on Saturday the 24th. It became for frequent and more regular. I only drive the car on the weekends and usually about 10 miles so I figured it would be fine until this weekend when I had a chance to replace the coils and spark plugs. Well, last night I heard a hissing sound that stopped and about 5 miles later I started hearing a metallic pinging sound that is 100% consistent. It does not speed up when I accelerate. The car is lagging horribly and it’s shaking so bad it feels like the motor wants to come out of the car. Now back on the 2nd of March I had an oil change done and the serpentine belt and fuel filter was also changed by Ford. What the hell did I do to my car?? If I understand the other postings correctly, a misfire in cylinder 6 doesn’t digress I to complete engine failure in under three weeks averaging 40 MPH over 10 miles? Any help is appreciated.