I do live here as such, but I am a permanent resident. Permanent resident status is granted only after many years living in Japan. There is no resident status of independent trader. Sorry for the bad news.
As an independent trader you wouldn't need a visa unless you went to the authorities and explained that you were earning a full time income from trading, and in that rare case you could sponsor your own visa. I guess if big $ were involved they would eventually catch up with you.
IB charges $1 per hundred so $1.50 isn't bad at all - especially considering that you can trade all day without worrying about the PDT rules shutting you down after doing 3 trades.