With two Notices To Comply having been issued and the police having been called, I think it’s time to ramp this up to the next level and apply to your local court for a Noise Abatement order.
That is a much more powerful instrument than a CTTT order in that it is a criminal offence to breach a court order and the police can arrest the miscreant if they do so.
Download and have a look at the document Dealing with Neighbourhood Noise and this one – Seeking a Noise Abatement Order.
Fair Trading and the CTTT aren’t particularly well equipped to deal with “domestics” and the process can be long and stressful with no guarantee of an acceptable outcome.
Gather your evidence (including police reports) and, with the support of the Owners Corp and individual owners, you can get a quick and effective solution through the local courts.
Regarding the unpaid levies, at the first sign of any such “retaliation” you could point out that not only are they subject to a mandatory penalty interest charge of 10 percent, they are also liable for all the reasonable costs of debt recovery, including the charges imposed by a debt recovery agency and, if necessary court costs. If they still won’t pay, you can garnishee the proceeds from the sale of the unit so that the Owners Corp gets paid before the money even hits the bank.