[samurai007]

1) I'd suggest more than that, at least try to budget $15-20 a day for food to be on the safe side, and to allow you to eat more than the very cheapest junk food like instant ramen. Decent quality food will probably cost you about $4-5 for breakfast, $5-6 for lunch, and $6-9 for dinner. And that is not for anything even approaching fancy, just simple stuff like okonomiyaki, ramen, domburi, yakitori, yakisoba, tonkatsu, etc. You could get away with a $10 day here or there by eating only 2 meals, or eating really super-cheapo stuff, but I don't think you'd enjoy the food very much day in and day out, and Japan has such great food, it would be a shame if all you ever ate during a month-long trip was the instant ramen and mos burgers.

4) I'd recommend leaving Tokyo, at least for short trips, to see the best parts of Japan...