It wasn't a matter of wrong vocabulary. It was a matter of wrong grammar. "Grason" is the accusative and since it's the object of the preposition "kun", it should not be in the accusative. It needs to be "graso".
Yes, although some would argue that there are subtle, nuanced differences between the two. I think the amount of difference depends on what you're negating, but that's my educated English-based instinct.
I remember it because I've also studied French, and the French word for meat is "viande". https://en.wiktionary.org/wiki/viande
It's ultimately from the Latin "vivere" or "to live". And meat comes from animals, who are alive.