I suggest starting with the following support article: If your iPad won't turn on or is frozen - Apple Support
If that doesn't help, it appears, from what you posted, that you have already tried everything you can do to resolve this yourself. At this point, I would suggest that you consider making a Genius Bar appointment at your local Apple Store or Apple Authorized Service Provider to have them take a look and provide you with your options for a potential resolution. Alternatively, you can use the "Get Support" link in the upper right-hand side of this forum's web page to get started.