Can an international PhD Student in Australia make a living with an APA scholarship and 8 hours teaching work per week?
I'm a current PhD student at the University of Melbourne. I can just support myself and one other person on my $30,000 of scholarships. I also live with just my partner (no housemates), our rent is just under $400/week + bills. So if you are OK with a more student-like experience you are likely to be fine, and use TA work to save for flights you need to take back to Europe.

Your estimate is quite low for TA work: the minimum wage for casual cafe or fast-food workers in Australia is over $22/hr. I get $44/hr for TAing, though this may just be Melbourne Uni. Also scholarships are tax-free, meaning you may not have to pay any income tax (as it would be nearly impossible to earn over the $18200 tax-free threshold given visa restrictions).