Mause I/II Questions

We see a variety of different animals used throughout both volumes of
Maus, with the intention of representing certain races of people. Polish
people are represented as pigs, with the French as frogs (though we see
him wanting to change Francoise from frog to Maus in part two, once she
converts), American dogs, Germans as cats, and the Jews as mice. What are
specific reasons behind each of these? In addition, why do you think he
doesn't stick to a purely religious/purely racial depiction? Does
portaying all of these characters not just as animals, but as cartoons, an
effective method? I think that it is, partly because it adds to the
symbolism in the novel, and partly because portraying people in
cartoon-animal form is a little less harsh than making them people. It
separates them a little, simply because cartoons are like caricatures by
nature.

My second question regards Art after the publication of Maus. He has
difficulty coping with the amount of success that the book has, we see him
undergo a sort of breakdown in Maus II, amidst a flurry of TV reports and
interviews. Why is this so? Shouldn't he be happy with the success he has?
Part of me thinks it's because of his relationship with his father - in
book form, Vladek's story is being lauded as a literary landmark; however,
Art would say it was less than so. Perhaps he regrets not developing a
better relationship, and displaying what they did have for the world to
see? Any other thoughts?