It does sound like you may have several issues. The P0410 code is usually the contacts on the air pump relay on the RCM. That system runs about two minutes at the start up of a cold engine. I doubt it would be producing your exhaust fume smells, but the code and problem should be addressed and corrected. I had a 2098 code which motivated me to get under the car and find the converter leak.
I read in another post that you made some repairs to the valve cover breathers ( the smaller covers on top of the valve covers) and you mentioned some broken screws. Definitely inspect not only the breather covers, but your valve covers. If you had broken the seal on the valve covers and then retightened them without completely removing the cover and cleaning the mating surface you could easily have a leak on the main valve covers especially at the rear lower edge. OF COURSE that is the most difficult area to inspect. Even when the car is not running there will be a puddle of oil along the bottom edge of the value cover, so there is always oil in that location ready to seep out of the valve train and out onto the exhaust. You will have to discount the fuel line in order to get the value cover off the engine to completely clean that mating surface. If you get that far I would use a new gasket upon assembly and put a very thin wipe of Permatex #2 non harding gasket sealer on the lower half of the mating surface as added protection against seepage/leak when reassembling. The upper half of the mating surface of the value cover does not have the standing oil behind it so I felt comfortable without the Permatex above the standing oil. As originally assembled only the gasket is used to make the seal between the value cover and the engine. Many people do not use the Permatex and have had good results. Be sure you use a good torque wrench and set it properly when reassembling all these covers. I used stainless steel screws with allen heads and they all use very little torque when tightening. Sorry I don't remember exactly what those torque specs are.
GOOD LUCK.