The past is the past. Stop looking back.
It doesn’t matter if you gave them a bloody kidney they don’t owe you and he does owe you.
All that matters legally is the now.
Right now you are the non resident parent. That’s all. Fact.
History changes nothing in these cases. You can’t and won’t win because he now has both children more than you. It doesn’t matter that you carried and birthed them it doesn’t matter that for the first 5 years you did 100% then 50% and now less than 50%.
Each section in time counts as its own it doesn’t build up as a debt owed to you because he was once shit.
All they the courts the cms care about is right now, and right now he has one child 80% so you owe maintenance and he gets CB, he has the other child 58% so again you owe maintenance and he gets CB.
If you had them 80 and 58 percent you’d be shouting about it being owed to you just as you were at 50%.
Time to reflect and maybe have someone to actually talk to because this level of believing your right when your wrong isn’t healthy your loosing your children over it. That should matter more than the money ever did.