Fridge Logic - One episode featuring a seeing eye dog said that after about 6 years most of the dog's training would've been forgotten. They later go on to say that the dog's training would hinder its ability to hunt and it would eventually starve to death. If the dog's training was so strong that it would impede its hunting ability, then it wouldn't have worn off at all by this point. Also, many other dogs would have to relearn their hunting instincts, so there's no reason a seeing eye dog couldn't too, especially if its life depended on it.
This is mostly a subversion for Labrador Retrievers. The reason why don't have the hunting skills of a canine is not because they are trained to be one of the friendliest dogs, but mostly because of their physical structure compared to other dogs.
The seeing eye dog was introduced as the only dog in the neighborhood who 'not only has been inside a supermarket, but knows the way there by heart'. Unfortunately in most cases the dog would be waiting outside by the curb for a bus or taxi that never arrives.
Initially, maybe, but seeing eye dogs are not robots, and they can ignore their training perfectly well if they really want to, as any person with such a dog can tell you.
It is also not entirely unheard of for a blind person to simply walk to the nearest shops if they live close enough. The series simply followed one of those.
Why are only the living people taken out? Mummies and modern preserved bodies are left for us to see how they rot.
They're already dead. Only live humans would abandon Earth in this show, not dead ones.