trying to establish what his income contribution to the relationship should be based on
It's not just about income, in two words it's about time & circumstance .... time as in length of relationship (very important), circumstance as in assets involved, children, business, superannuation etc etc...
Very basically, there is a 4 stage process in property settlements
1) Establishing the nett asset pool (all assets, savings etc) & it's value
2) Contributions made to the above (financial & non financial)
3) Future needs & warranted adjustments
4) Practical affect of settlement orders on both parties..
I recommend he visit a family lawyer with all the facts & figures to get an educated opinion on what each parties entitlements may be, & with that information, then arrange an accredited mediator that can help them both reach an agreement that they can then convert to orders by consent.... That's the fastest, least expensive approach, & requires minimal lawyer involvement..