Hello and thank you for your question.
If you have been living together as a defacto for more than two years then you will be subject to the Family Law Act, which means upon separation your assets are subject to division in much the same way as if you were married. That essentially means that a court, upon an application by either party, will divide the combined marital asset pool on the basis that each party is entitled to a fair share having regard to their respective contributions, and then adjusting for any special considerations such as where one of you will be caring for a child of the relationship, or where one of you has serious health issues which affect that person's ability to support themselves.
Absent special factors, the main consideration is what each party contributed financially. As it sounds like you have contributed more than your ex, you will likely get a much greater share of the assets, and if as your description implies, your ex effectively only brought debts to the relationship, you may be entitled to the whole of the asset pool, however, if your partner is still in debt a court is unlikely to force him to borrow more to 'pay you back'.
Only a fully briefed lawyer can give you a firm answer as to the amount you will likely recover, however I trust my answer assists your understanding as to how the law applies to your situation.
Good luck and please rate my answer.