Yep, you have to wait the two years. The no career opportunities makes no difference. As long as you are doing the job sponsored for immigration doesn't care as you are doing what was agreed. As for the extra hours, if your contract doesn't say you have to do extra hours then you can say no. Fairwork Australia can help you with what they are allowed to and aren't allowed to do. If they are making your work life hard then document EVERYTHING. They have to be following Australian employment law. If they are not then you don't have to stay, but you must be able to show you have done everything in your power to correct the situation and haven't just up and left.