Sorry you have to deal with such an awful organisation. Obviously the MD has no regard for the tenancy laws, complaint resolution or your health as tenants.
I'm guessing they won't renew your lease... If they are as useless as they sound then you'll move to a periodic lease and they'll serve you an eviction notice when they are ready (or not)
You still have rights and don't need to go anywhere until they get a possession order via the tribunal. You can still dispute this.
Make sure you have written and photographic evidence of your claims, emails, texts, receipts, water bills.
Get some help from your tenants advocate https://lsc.sa.gov.au/23
They can help you seek compensation for all these breaches yourself via the SACAT
Focus on the RTA breaches but also ask for some info on how to address their breaches of the Estate Agents Act (and if it's worthwhile)
If you have evidence of your agent bad mouthing you to other agents and it's not true then you also have a potential defamation case (you may need to paid legal help if you want to pursue this avenue).
I know it seems overwhelming but don't give up - it'll be worth it in the end.
Sorry I couldn't give you more specific help as I'm from VIC but at least you have an idea of the basics.