I'm sorry to hear you're having a rough time at work.
My work environment isn't particularly perfect at the moment either.
At my last OB appt, he asked what date I was planning to go on Maternity Leave, which is was at 37 weeks. I got a little teary and confessed that work was incredibly stressful, very demanding, and that I was feeling terrible about going to work each day.
He told me that that kind of stress was very bad for me and the baby, and has written a sick certificate to leave two weeks earlier. I would have like to go earlier again, but due to sick leave entitlements plus work commitments, didn't think it was fair to just up and leave (trust me.....I DREAM of it every half hour).
You could always have a look at this avenue. You could look at it as a short term measure (take a couple of days off, just to calm down a little) or as a long term, finish up early to start unpaid/paid maternity leave.

As for your other entitlements - Annual Leave and Long Service Leave (if applicable), regardless of if the business decides to close up, you are still entitled to every single cent. An employer is obligated to pay out ALL employee's entitlements, including any unpaid super contributions as a matter of priority. State Governments have various schemes in place, as well as the insolvency laws to protect you in this instance. My only other comment would be NOT to agree to any alternative payment in lieu, just stick to what you are entitled to.

Good Luck, and I hope it all turns out OK