1. What do animals eat?
Merenwe and I talked and decided that for meats, insects, fish, clams, shrimp, mussels, oysters, etc. are acceptable. Of course any edible plant is allowed. What we will call "cannibalism" is allow to a very very specific degree, since it is included in a few of Brian Jacques books to a degree. If you desire to RP a cannibalistic character, this will have severe ramifications in everything else they do. Even hardened villains will shy from a creature who eats others. It is taboo, and those who break the taboo will either be slain or will have to constantly adapt and avoid being killed by virtually anyone they might encounter. If you choose to RP as a character who is a cannibal, you will need to thoroughly discuss it with Merenwe and I first, and it is highly likely that the RP thread would result in the death of your character. I can see very very few things that could happen instead of death.
3. Predators have been on the mainland for time out of mind. I think they'll be treated reasonably by almost any character, since we now have the established "meat" rules. This doesn't mean that character will not base their snap judgements of others based on their experiences, because they will. So someone who's had a bad experience with a certain species will most likely be more leery of them.
Example: My character Niamh feels very, very self-conscious and nervous around other otters, and much more at home around hares. She struggles with feelings of resentment towards her family, which can come out sometimes when dealing with other otters.
I'm afraid I have no answers for your other questions yet, but we're working on them.