After another week, and the oil smell does not seem to be coming back. Additionally, unscrewing the oil cap and trying to pull it out while the engine is idling shows that there is now a vacuum in the crankcase too, which indicates that the blowby issue has disappeared! The compression pressure seems to be about the same, roughly 155 psi when warm, so I don't know if that's going to improve any further, but the crankcase vacuum is still very encouraging.
Additionally, the "new" used Mazda 6 wheels now have tires and are installed (although Discount Tire really screwed up the fresh paint on them - they handled the painted winter wheels for two other cars fine, but these got really beat up), the brake system is flushed, and I went through the various plastic panels and heat shields to add foam and other sound-deadening material. At this point, Kaylee is feeling like a new car!