This is a great thread, a few random comments:
I won't be worried about eating Polar Bear livers, over-rich in vitamin A. A Polar Bear is a T-Rex in a furcoat, he can keep his liver. Way outside my survival area.
However, back in the '40s and '50s, my Mom served up a dinner of beef liver and onions once a week. Cover it with ketchup, which is a vegetable

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Eating all of the animal: This may be an apocraphyl story, but I read it once and a VietNam vet confirmed it for me: The Montagnards would kill a wild pig and then throw the whole thing on the coals...fur, hide, guts and all, no gutting or cleaning...roast it in its own natural juices. My Viet vet friend said it was great eating, although I bet he passed on the guts.
I think every culture in the world has a tradition of eating organ meat: liver, kidneys, heart, brain, blood pudding, chitlings (intestine). My grandmother was feeding me liver and chitlings before I knew enough to think about being disgusted. Given Mad Cow disease, I think we all would pass on brain today. Otherwise, I have no problem with organ meat.
What wild vegetables and fruit are safe?: Depends on where you live, of course. Here in the Northeast, I eat the flowers and leaves of dandelions in the spring and the leaves all summer long in salads, sandwiches, etc. Same thing with wild violets, wild raspberries, strawberries, blackberries, blueberries, elderberries, wild apples. Also Day Lily buds and blossoms and cattail roots. As far as mushrooms go, there are puffballs and morels, they cannot be confused with anything else that I know about. Milkweed pods are edible but take a lot of boiling.
We have all the regular North American wild meat game.
I have eaten Beaver, the four-legged kind (I know, there's still a joke there). My friend is a trapper and for a couple of years was supplying me with a few beaver carcasses to experiment with. I made stew, chili, jerky, broiled it, etc., and I have to say it is strong flavored. But definitely okay as part of my survival diet.
Haven't tried muskrat yet, which is another thing he traps. People have been know to eat rats (shave tail squirrel), mice, lizards and snakes. Turtles and their eggs, of course. Minnows (sardines). Birds are a no-brainer.
I think the one thing that grosses me out is blubber, just to think about it. I know the Japanese and some Inuit and Scandinavians love it. I'll eat anything once, just haven't had the opportunity to try that.
Survival food at sea: Well if you're lucky you might get a few flying fish landing in your boat. Fish can be eaten raw (sushi) and the meat will provide you with some water.