Seeker, I'm not a pro mechanic, but lets see how close I get to what you find is wrong in the end. I think your oil sensor is failing , as you thought. Don't know where it is. The run rough symptom is trash in the carb or injection system. Sea foam is a great product used since the 40's. Just follow the directions. If that's not it then I think you may be dealing with some ethanol damage problems. It damages the rubber parts and other things throughout the fuel system. Were it mine I would take it to a REPUTABLE pro. Just cuz they're close don't make em good. You may have to drive some to get to one. Again, I'm not a pro. Just read all I can and pay attention when smart people talk. Blue sta bil helps a lot with the ethanol damage prevention. Please keep us posted on what solves your problem.