Hello Tien,
There have been some instances where employees have been bullied because their boss knows they have leverage over them through these types of visas (conditional visas). This behaviour is also exacerbated by workers showing fear rather than standing up for themselves.
First your health must be a priority not your visa or employment, i understand that this is not easy for most people but you are in luck because Australia has a strong and independent Judicial system that does not tolerate bullying anywhere including the workplace. The FWC is Australia's national workplace tribunal that regulates employees and employers. You should direct all concerns, complaints or unfair dismissals to them regardless of your visa the law doesn't discriminate against employees based on their work status in Australia as long as they are legally allowed to work.
You shouldn't resign without documenting what's going on and have at least some evidence of workplace harassment or bullying. The best way to document and have evidence of such events is to contact the FWC and make a formal complaint if need be. With such evidence it becomes hard for DHA to cancel your visa because you can show that you had a compelling reason to resign. You can also visit a Psychologist or a doctor if the matter is serious enough which can also be used as evidence. With that said i would advice showing strength while remaining composed and respectful towards your employer.
However your employer sending you to another venue because you think he doesn't like you ....doesn't seem like a compelling reason to me to breach your visa conditions. If its just a matter of not liking each other than that is not serious enough and you should wait until your ceremony or the 24 month mark whichever comes first.
Take care