1) I worked in IT in Japan for 2 years, have been working in the states for 10 years, and I've got my education in Japan. IT field kind of sucks in Japan for hardcore programmers, people with the degree from MIT in CS usually don't want to work in Japan. But it is not hard to get in, and as you speak English fluently, you will be handy in American and other foreign companies. If you don't mind management side of the business in the future like in 10 years, and want to work in a different culture, working in Japan can be an option. If you are more techy type and like to code big applications with C, C++ and/or Java, I wouldn't go to Japan with your background.
2) I don't think it is hard to make $45k in Japan, I probably made that much in my second year, but you need to work really long hours. You might hope you would make less and work less, but for some reason, that's usually not an option.
3) My major was International Culture. You get the idea.
Anyhow, good luck to you.