[WingsToDiscovery]

Not to tread on your dreams mate, but your chances of living here legally are zero.
In order to live here you need a degree (99.9% of the time), and to have a degree you need a high school diploma or equivalent. It doesn't matter what your degree is in to become a teacher here, but it's what you need to live here.

To be honest, you seem like you've had some really rough patches in your life, and the most responsible thing you can do right now is get back on track for your own sake, rather than with the hope of coming to Japan. If in a few years you end up getting a degree and are eligible to come over here, then that's great, but right now that should be the least of your priorities. Figure out how to get some sort of diploma first. Then figure out how to get a degree (anyone can go to college, there's all kinds of financial aid and other benefits for students, and you can get in with a GED). This is all for your own good. It's hard enough to survive in America without any sort of diploma or degree, let alone trying to move to Japan.

If after all of that you think you're ready to come over to Japan, then go for it.