Wrong fuel put in the tank

My husband recently put diesel fuel in our car listed above. He is seventy five years old and has early dementia. When he finally noticed he put the wrong fuel in the vehicle we had someone drain the gas tank and clean out the gas lines. We changed the spark plugs and cleaned the fuel injectors. We put premium unleaded in the tank after we did that and put seafoam in the tank. There is white smoke coming from the tail pipe. The vehicle is not idling right and if you try and drive it it loses power. It will shut off on us but it will start back up with the same symptoms. The check engine light came on when this happened but we took the battery cables off the car and waited awhile and put them back on and the check engine light went off. When the check engine light first came on it was reading misfire. What else could be the problem? They also checked the oil filter on the rail and it said over fifty percent. Please reply.