Your lawful status depends upon your continued employment with your employer. Once you quit, your status effectively ends. When you quit, your employer is obligated to inform USCIS that you are no longer working there. At that point, USCIS will revoke your petition approval.
If you accrue more than 180 days of unlawful presence, you are barred from reentering the U.S. for three years. If you accrue more than 360 days of unlawful presence, you are barred from reentering the U.S. for ten years.
