(mostly dead by the time we eat them).

This is flawed logic. Would you say the same if I was into watching child porn? I mean, it's already happened, so it makes no difference if I watch it.

About the best way to ensure fewer animals are killed to become food for us to eat, would be to eat those animals more efficiently ie eat every part of the animal.

You think that eating the entire animal is more efficient than directly eating the plants? Instead you recommend we feed an animal that converts about 10 pounds of plant into a pound of steak, rather than eating the plants?

Another way to reduce the moral cost of eating animals would be to eat animals lower in the food chain.

Even better, eat lower in the food chain than the low animals? No? You're telling me you'd rather eat roaches than a bean burger? Blows my mind.