Don't mean to be rude.
Have you spoken to your countrymen at your work place and see how they get along.
If all are in the same boat, why not approach your embassy, are they not here to assist you? The first point your embassy can pick on is the change in contract. Working hours etc etc. Go to the NHRC.
Repaying your sponsor is out of the question.
If you are really not happy, better to find another job, go on vacation and do not return.
Sorry, venting your sorry, may alleviate some of your pain, but you need to take action to remedy the wrong you have been put through.
Or, be thankful for your plate, it could have been worse.