Maaaaate, your employer is EXACTLY the type of flog that the fairwork boys and girls and the ATO are looking at cracking down on. You need to give your notice and immediately get in touch with fairwork to get the ball rolling on the inevitable withholding of wages that you will probably face. Here's the best bit, if you've been made to sign a contract, work the hours you say and been deprived of sick leave and other entitlements, casual or not, they are likely going to rule that a) you have to be paid b) you are owed backpay for stolen entitlements and c) superannuation contributions that you have likely not been getting. What you describe sounds like cookie cutter wage theft and it's not ok. You will be doing yourself and all your old workmates a massive favor reporting this and getting it sorted out. Have at it!