I would be grilling the son about how car came to be that way, pretty uncommon to show up like that suddenly since you have already serviced the parts likely to have fixed a sudden issue.
If you have tried to start it enough the not running will positively wet the plugs out to then not start easy and die easy. Pull them to see if they are wet. Your perceived rich issue, ALL cars start rich but go to running fast enough to burn the plugs off clean, if they cannot run due to other reason the plugs quickly wet out. Then car only runs like crap for a second to die even if nothing is wrong with it. May need more plugs.