Automatic Emergency Braking problems of the 2014 Cadillac CTS

Burning smell, traction control, rear axle service along with suspension lights all came on the odometer. Shakes at low idle and wont stay running. Happened this weekend after pulling into the driveway after driving. We scanned code for cylinder 4 misfire. On scanner we had multiple other cylinder misfires but cylinder 4 is a dead misfire. We removed spark plug and found wore. We initially thought to start with replacing spark plugs and cylinder 4 coil. We consulted with customer and agreed to replace all spark plugs and cylinder 4 coil. After replacing we found no change in cylinder 4 misfire. We removed and re installed original coil and re tested. We performed a compression test on cylinder 4 and have 0 psi. We thought possible carboned valve stuck open due to direct injection system. We performed a gdi carbon clean but still no change. We installed a borescope into cylinder to inspect and found what looks like a broken piston or part of a valv we scanned code for cylinder 4 misfire. On scanner we had multiple other cylinder misfires but cylinder 4 is a dead misfire. Weremoved spark plug and found worn. We initially thought to start with replacing spark plugs and cylinder 4 coil. We replace all spark plugs and cylinder 4 coil. After replacing we found no change in cylinder 4 misfire. We removed and re installed original coil and re tested. We performed a compression test on cylinder 4 and have 0 psi. We thought possible carboned valve stuck open due to direct injection system. We performed a gdi carbon clean but still no change. We installed a borescope into cylinder to inspect and found what looks like a broken piston or part of a valve broken and smashed into the piston. Fault is internal engine, would need to tear down and re build or replace engine assembly. My safety was at risk driving 80mph on the highway perhaps engine could have seized or caused problems I’m not able to deal with along with having my infant and toddler in the car.