Found a way to pay my own way (PMOW, heh) concerning child support in my country. In short it's finding ways to get tax free money. This put the control in my court. Not sure if this works in every western country. One of the main ways one could do this (not the way I do it. My method is too unconventional to work for the average guy) is to setup an offshore company outside the economic jurisdiction of your country.

This is quite easy to do: https://www.sfm-offshore.com

So I tell the ex what I want to pay for, say 1/2 of private school fees for example, and ask for the bill.