I've read far too many posts where employers are shorting paychecks, overtime, requiring too much information, changing vacation last minute, and the list goes on.
They do not have the upper hand. They make it sound like they do. They have all these rules you must abide by. But the fact of the matter is that you have the upper hand. They need you.
Be firm with your personal boundaries. Your sick day is not an option and you don't have to tell them why you're sick. Don't accept working without proper pay. YOU DO NOT NEED TO GIVE THEM A TWO WEEK NOTICE!