On the culture question, it's not a matter of how involved the father is in his Indigenous community, but rather, it's about ensuring the children enjoy the opportunity to learn about his cultural traditions from the relevant parent. If you're not Indigenous yourself, then obviously this part of section 60CC benefits dad, not you.
I'll be honest.
If two of the four kids are on 50/50 now, there's a pretty good chance the Court will order 50/50 for all kids, or at least very close to it.
I say this for a few reasons.
First, there aren't a lot of circumstances where arrangements will go from 50/50 agreed or ordered, back to alternate weekends and half holidays at final hearing. Unless you have incontrovertible proof that 50/50 is hurting the kids, the Court would be reluctant to change the status quo, and it would be reluctant to have all four kids on different care regimes.
Second, it's entrenched in law that the Court must first consider equal time where the presumption of shared parental responsibility is upheld, and failing that, it must then consider substantial and significant time. Substantial and significant time is a combination of weekdays, weekends, holidays and special occasions, so the old-school every-other-weekend deal doesn't really exist where shared parental responsibility does. If it's not 50/50, substantial and significant time is in all but a rare few cases, considered four, five or six nights a fortnight.
Third, the one-year-old should be well and truly on to solids as his main source of nutrition, now, and that's not a matter of opinion, but more a matter of medical research. On top of that, if the siblings are with dad 50/50, the toddler is probably more likely to cope with the care arrangement, but if the Court wants to address any doubt, it might increase time in increments until the toddler is on the same care arrangement as the other kids.
Fourth, I've read a lot of your posts, and from what I can't tell, you haven't provided any real compelling reasons why 50/50, or close to it, isn't viable. Sure, you've got AVOs against each other, but this is family law. AVOs are a dime a dozen, and judges have even remarked to press that there are more family law cases with AVOs involved than without, yet only a very small percentage actually find the allegations of family violence compelling as an influencing factor in parenting matters.
You've asked when it gets better. In my experience, it gets better when the parents lay down their arms. My husband and his ex had an extraordinarily volatile relationship following separation. Like your ex, he wanted 50/50, and like you, she wanted him to have three nights a fortnight, which was granted in interim orders. There were over 10 incidents where police were called, one AVO pursued by her, two by us, countless arguments in front of and even involving the child, then just four years of age, and even physical disputes sometimes, yet in the end, they still ended up with 50/50.
After they'd finished with Court and their fifth matter was closed, they very slowly, piece by piece, started working as co-parents, and now things are very amicable. I wouldn't describe them as friends, but they certainly respect each other and the important role they each play in their daughter's life.
What changed was them laying down their arms.