Jambi, you need to apply for a new job. Your current employer is snowing you. A starting rate even for a new grad ought to be 40%, and you can get that rate easily enough with all the bells and whistles of being a full time employee.
50% is common for ABN holders, although there are plenty who are on this rate and still get holiday pay super etc.
31% is dismal by any standard.
Shop around, get an offer and tell him/her what you want .