The split will be what you both agree to... or if a Court is left to decide... then it will be as decided by the Court.
Many factors (set out in the legislation) are required to be considered before a % split of the joint marital asset pool (which includes both your superannuation balances) is decided by the Court.
The fact you were together 18 years, means that what you brought into the marriage will have a much lower weighting, if there was a difference... than if you were married only a short time ago...
The fact you have a disability, also means that relatively speaking you will not only have greater future care needs, you may also have less earning potential... which (everything else being equal)... should result in the Court awarding you a higher share of the assets.
Please read the following prescribed reading issued by the Court which outlines the process that is required to be followed prior to any Court action regarding a property settlement:
It is possible to agree outside of Court - but you must both first obtain certificates of independent legal advice before you sign any Binding Financial Agreement (known as a BFA).
If you can both agree, another alternative is to lodge consent orders with the Court for its approval.