I would recommend you to keep records of everything that happens at work and causes you stress and tears. Also you can email your boss (always written communication that you can recover in your inbox, instead of just paper that can be destroyed) and talk to them. If things dont get better and you leave your job, if the immigration decides to investigate you will have proof that things weren't good there for you. Also keep a good relationship with other staff members even if you leave your job so they can support you if something happens.
If you have been in australia so many years in a few months you will get citizenship so by the time the start investigating you might be a citizen already.If you ask most of the migration agents, they cannot tell you what is gonna happen with your case but they will definitely say that they have never heard of anyone losing their pr.
Best of luck my friend