I suppose the sentence means that "The merchant sells various kind of meat". Otherwise caro would have been used in singular.
Yes, but it is given that a merchant who sells meat sells various kinds of meat.
Of course, that's the obvious truth. I was just stating the difference in meaning between carnes (which is used in this sentence) and carnem, to justify the given translation.
I don't think it's a given unless the sentence gives context for it (eg. fish and beef).