Hi,
If you explain to them that the 45 days you spent in Sydney were just for work (I assume that's what they were for?) but that you consider Vic to be your home then I reckon you should be ok. Your best show of a commitment to the state is if you have a job already there or one lined up, include the contract/offer with the letter. I would also say why you love Vic and why it is home, give examples of how you have integrated into Vic and how settled you are there eg commitments other than work.
Good luck