Let your lawyer handle it. Do not discuss this stuff with him at all as he does not have yours or your kids best interests at heart so anything he says or tries is for his benefit.
60/40 has nothing to do with custody arrangements. It's about disparity in income and future earnings - plus if you've been a SAHM or part-time your future earning capacity has been impacted.
60/40 is generally the standard split in Australia as spousal support doesn't really exist and Child Support is laughable. I get $8k per year when he earns c$250k+. If I had the girls full time that would increase to $15k which is a joke. This figure is Australia-wide so does not tke into consideration that Sydney is faaaar more expensive than the rest of the place.
The calculator stops at $120k so I could pursue him if I needed to but he's paying all school before/after school expenses so it works out for me. If he refuse to pay I could get it via CS adjustment based on special circumstances of a) his income being more than double mine; and b) additional costs outside the scope of "normal" costs.
CS doesn't have anything to do with asset split.
DO NOT PANIC unless/until its time to panic. He can try on whatever bullshit he likes. You could go at him for costs if he fucks around too much.
I asked my L for a worse-case scenario (what a court would award) - once I knew that I wasn't as fearful. It has ended up being that worst case scenario because he is a fucktard who is hell bent on destroying me financially becaus he didn't quite manage to destroy me emotionally.
Keep emotions out of it - you won't get vengeance or justice and neither will he, no matter how hard he'll try.