AFAIK, he said he will continue until 2012 Words in Nice, France at least. And after that I guess it will depend on how he is skating and feeling, and he may decide to continue until 2014 or retire after the worlds in his home country.
4 I don't know but based on his words probably definitely 2 more years. He'll be 30 for Sochi I think. Others have come back at 30 like Boitano, Eldridge, Stojko.
We see so many 30s among Olympians so it won't be a big deal as long as he stays healthy and remains cute and maintains good sponsors (All three factors seem to go hand-in-hand).