I can offer hope and ideas for navigating the most difficult co-parent behaviors. Divorce is hard on everyone, please don't use your former partner as a target for your rage and frustration.
As our kids grow up, our past transgressions and lies will come back to haunt us. I don't think I've lied to them, other than the agreed upon lie (giving my wife the all-important cover) that the divorce was a mutual decision. It was not.
Marriage and parenting start at 50/50. Divorce should start at 50/50 without child support, and negotiate from there.
You can't have kids by yourself. Your partner is just as important. Why would it be different when you no longer live together?
In some twisted way, my ex-wife assumed that she was the better parent and thus more entitled to the child support, the house, and the kids' care and feeding. As a good dad, this was just her assumption. Today, her assumption wound probably be supported by state family law. But, I believe times are changing.
Not a percentage of salary earned. No, she believed, still believes, that the child support is her entitlement. This is no longer a relationship it's just a business contract. I am no longer a person to her, I'm a debtor. I'm the problem. I'm the reason she's unhappy.