The weird smell keeps catching my attention too. Most oils that are burning in an engine smell about the same and i'm sure we've all smelled them enough to know the scent.
Can you pull a fuel sample and take a look at it in the sun for color? Take a whiff of it too? Try filling the carb with fresh gas for a short run to see if it clears up any?
You mention the plugs are kinda black, are they sticky/gooey too, like from some kind of contaminant in the fuel system?