The smell could be a lot of things. After about day 1, ground pork will tend to start getting "sticky". On the second day, it already begins to smell a little. As far as I'm concerned, by day 3, it's unusable. Also, because retail stores inspections are few and far between because of being understaffed, it may be that they didn't properly clean their grinder. Another possibility, though remote, is that the pigs slaughtered were in "heat". Sexual odors are excreted throughout the bodies and stress before slaughter can also cause the muscle to take on strange odors. It could also be numerous bacterial contaminants. Not every one gets drastically ill from contamination, so you may have got lucky.
As for fat ratio, unless it is a wild boar, it will not make a difference. Ground beef will not help either, as it will either become "smelly" too, or mask the odor, which doesn't solve the underlying problem.