First time I brewed a German lager it just smelled aweful during the primary fermentation. I mean, it was the worst smelling beer I've ever brewed. I don't recall the yeast strain and that would be home in my notes somewhere, not here at work. Anyway, visited a forum like this one and did some reading. Lagers can produce more sulphur compounds than ales and smell bad depending on the strain. Beer eventually turned out just fine and friends liked it. The yeast took care of whatever created the smells during the fermentation.
That doesn't explain the sluggish fermentation. Maybe you cooled too fast and the yeast crashed? Maybe you could rouse the yeast or repitch. I'm too cheap to just dump a batch with out trying something to kick start it. Unless there's something obvious and visually wrong (other than the odor) maybe you could repitch and see what happens. Oh well, you can see and smell the brew and I can't...so, best of luck.